Electret-containing filter media

ABSTRACT

Filter media, such as electret-containing filtration media for filtering gas streams (e.g., air), are described herein. In some embodiments, the filter media may be designed to have desirable properties such as stable filtration efficiency over the lifetime of the filter media, increased normalized gamma, relatively low pressure drop (i.e. resistance), and/or relatively low basis weight. In certain embodiments, the filter media may be a composite of two or more types of fiber layers where each layer may be designed to enhance its function without substantially negatively impacting the performance of another layer of the media. For example, one layer of the media may be designed to have a relatively low basis weight and/or a relatively high air permeability, and another layer of the media may be designed to have stable filtration efficiency and/or a relatively high efficiency throughout the filter media&#39;s lifetime. The filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment), though the media may also be used in other applications.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/438,042, filed Feb. 21, 2027, which is incorporated herein byreference in its entirety.

FIELD OF INVENTION

The present embodiments relate generally to filter media andelectret-containing media specifically, to filter media including opensupport layers.

BACKGROUND

Filter elements can be used to remove contamination in a variety ofapplications. Such elements can include a filter media which may beformed of a web of fibers. The filter media provides a porous structurethat permits fluid (e.g., air) to flow through the media. Contaminantparticles (e.g., dust particles, soot particles) contained within thefluid may be trapped on or in the filter media. Depending on theapplication, the filter media may be designed to have differentperformance characteristics.

Although many types of filter media for filtering particulates from airexist, improvements in the physical and/or performance characteristicsof the filter media (e.g., strength, air resistance, efficiency, andhigh dust holding capacity) would be beneficial.

SUMMARY OF THE INVENTION

Filter media are generally provided. The subject matter of thisapplication involves, in some cases, interrelated products, alternativesolutions to a particular problem, and/or a plurality of different usesof structures and compositions.

In one aspect, filter media are provided.

In some embodiments, the filter media comprises an open support layerand a charged fiber layer mechanically attached to the open supportlayer, wherein the charged fiber layer comprises a first plurality offibers comprising a first polymer and a second plurality of fiberscomprising a second polymer, wherein the first polymer is acrylic, andwherein the open support layer is a mesh having an air permeability ofgreater than 1100 CFM and less than or equal to 20000 CFM.

In some embodiments, the filter media comprises an open support layerand a charged fiber layer mechanically attached to the open supportlayer, wherein the charged fiber layer comprises a plurality of fibershaving an average fiber diameter of less than 15 microns and greaterthan or equal to 1 micron, and wherein the open support layer is a meshhaving an air permeability of greater than 1100 CFM and less than orequal to 20000 CFM.

In some embodiments, the filter media comprises an open support layerand a charged fiber layer mechanically attached to the support layer,wherein the open support layer has an air permeability of greater than1100 CFM and less than or equal to 20000 CFM, wherein the filter mediahas an overall basis weight of greater than or equal to 12 g/m² and lessthan or equal to 700 g/m², wherein the filter media has a gamma greaterthan or equal to 90 and less than or equal to 250, and wherein thefilter media has an overall air permeability of greater than or equal to30 CFM and less than or equal to 1100 CFM.

In some embodiments, the filter media comprises a charged fiber layer,an open support layer mechanically attached to the charged fiber layer,and a coarse support layer that holds the charged fiber layer in a wavedconfiguration and maintains separation of peaks and troughs of adjacentwaves of the charged fiber layer, wherein the charged fiber layer has abasis weight of less than or equal to 12 g/m² and greater than or equalto 250 g/m², wherein the open support layer has an air permeability ofgreater than 1100 CFM and less than or equal to 20000 CFM, and whereinthe filter media has an overall air permeability of greater than orequal to 10 CFM and less than or equal to 1000 CFM.

In certain embodiments, the charged fiber layer comprises a firstplurality of fibers comprising a first polymer and a second plurality offibers comprising a second polymer. In certain embodiments, the firstpolymer and the second polymer have different dielectric constants. Incertain embodiments, a difference in dielectric constants between thefirst polymer and the second polymer is greater than or equal to 0.8 andless than or equal to 8. In certain embodiments, a difference indielectric constants between the first polymer and the second polymer isgreater than or equal to 1.5 and less than or equal to 5.

In certain embodiments, the second polymer comprises a syntheticmaterial selected from the group consisting of polypropylene, dry-spunacrylic, polyvinyl chloride, mod-acrylic, wet spun acrylic,polytetrafluoroethylene, polypropylene, polystyrene, polysulfone,polyethersulfone, polycarbonate, nylon, polyurethane, phenolic,polyvinylidene fluoride, polyester, polyaramid, polyimide, polyolefin,Kevlar, Nomex, halogenated polymers, polyacrylics, polyphenylene oxide,polyphenylene sulfide, and combinations thereof. In certain embodiments,the second polymer is polypropylene.

In certain embodiments, the second polymer is present in the chargedfiber layer in an amount greater than or equal to 10 wt % and less thanor equal to 90 wt % versus the total weight of the charged fiber layer.In certain embodiments, the second polymer is present in the chargedfiber layer in an amount greater than or equal to 25 wt % and less thanor equal to 75 wt % versus the total weight of the charged fiber layer.In certain embodiments, the second polymer is present in the chargedfiber layer in an amount greater than or equal to 35 wt % and less thanor equal to 65 wt % versus the total weight of the charged fiber layer.

In certain embodiments, the first polymer comprises a synthetic materialselected from the group consisting of polypropylene, dry-spun acrylic,polyvinyl chloride, mod-acrylic, wet spun acrylic,polytetrafluoroethylene, polypropylene, polystyrene, polysulfone,polyethersulfone, polycarbonate, nylon, polyurethane, phenolic,polyvinylidene fluoride, polyester, polyaramid, polyimide, polyolefin,Kevlar, Nomex, halogenated polymers, polyacrylics, polyphenylene oxide,polyphenylene sulfide, and combinations thereof. In certain embodiments,the first polymer is dry-spun acrylic.

In certain embodiments, the first polymer is present in the chargedfiber layer in an amount greater than or equal to 10 wt % and less thanor equal to 90 wt % versus the total weight of the charged fiber layer.In certain embodiments, the first polymer is present in the chargedfiber layer in an amount greater than or equal to 25 wt % and less thanor equal to 75 wt % versus the total weight of the charged fiber layer.In certain embodiments, the first polymer is present in the chargedfiber layer in an amount greater than or equal to 35 wt % and less thanor equal to 65 wt % versus the total weight of the charged fiber layer.

In certain embodiments, the first plurality of fibers have an averagefiber diameter of less than 15 microns and greater than or equal to 1micron. In certain embodiments, the second plurality of fibers have anaverage fiber diameter of less than 15 microns and greater than or equalto 1 micron.

In certain embodiments, the open support layer has a solidity of lessthan or equal to 10% and greater than or equal to 0.1%. In certainembodiments, the open support layer has a solidity of less than or equalto 2% and greater than or equal to 0.1%.

In certain embodiments, the charged fiber layer is needled to thesupport layer. In certain embodiments, the charged fiber layer isneedled to the support layer at a punch density of greater than or equalto 15 punches per square centimeter and less than or equal to 60 punchesper square centimeter. In certain embodiments, the charged fiber layeris needled to the support layer at a penetration depth of needling ofgreater than or equal to 8 mm and less than or equal to 20 mm.

In certain embodiments, the charged fiber layer has a basis weight ofgreater than or equal to 10 g/m² and less than or equal to 600 g/m². Incertain embodiments, the open support layer has a basis weight of lessthan or equal to 200 g/m² and greater than or equal to 2 g/m². Incertain embodiments, the open support layer has a basis weight of lessthan or equal to 50 g/m² and greater than or equal to 5 g/m².

In certain embodiments, the open support layer has a strand count alonga first axis of greater than or equal to 2 threads per inch and lessthan or equal to 27 threads per inch. In certain embodiments, the opensupport layer has a strand count along a first axis of greater than orequal to 3 strands per inch and less than or equal to 20 strands perinch.

In certain embodiments, the open support layer comprises a plurality offibers or strands having an average fiber diameter of greater than orequal to 0.5 microns and less than or equal to 2 mm. In certainembodiments, the open support layer comprises a plurality of fibers orstrands having an average fiber diameter of greater than or equal to 0.5microns and less than or equal to 10 microns. In certain embodiments,the open support layer comprises a plurality of fibers or strands havingan average fiber diameter of greater than or equal to 10 microns andless than or equal 20 microns. In certain embodiments, the open supportlayer comprises a plurality of fibers or strands having an average fiberdiameter of greater than or equal to 500 microns and less than or equalto 2 mm.

In certain embodiments, the open support layer is formed by a spunbondprocess and comprises a plurality of fibers having an average fiberdiameter of greater than or equal to 10 microns and less than or equalto 20 microns. In certain embodiments, the open support layer is formedby a meltblown process and comprises a plurality of fibers having anaverage fiber diameter of greater than or equal to 0.5 microns and lessthan or equal to 10 microns. In certain embodiments, the open supportlayer is a mesh and comprises a plurality of strands having an averagestrand diameter of greater than or equal to 500 microns and less than orequal to 2 mm.

In certain embodiments, the charged fiber layer has an uncompressedthickness of greater than or equal to 5 mils and less than or equal to600 mils, or greater than or equal to 30 mils and less than or equal to350 mils.

In certain embodiments, the charged fiber layer has an air permeabilityof greater than or equal to 10 CFM and less than or equal to 1200 CFM.In certain embodiments, the charged fiber layer has an air permeabilityof greater than or equal to 80 CFM and less than or equal to 1200 CFM.In certain embodiments, the charged fiber layer has an air permeabilityof greater than or equal to 50 CFM and less than or equal to 650 CFM.

In certain embodiments, the filter media has an overall basis weight ofgreater than or equal to 12 g/m² and less than or equal to 700 g/m². Incertain embodiments, the filter media has an overall basis weight ofgreater than or equal to 25 g/m² and less than or equal to 650 g/m².

In certain embodiments, the filter media has an overall basis weight ofgreater than or equal to 30 g/m² and less than or equal to 800 g/m². Incertain embodiments, the filter media has an overall basis weight ofgreater than or equal to 100 g/m² and less than or equal to 450 g/m².

In certain embodiments, the filter media has an overall thickness ofgreater than or equal to 5 mils and less than or equal to 600 mils. Incertain embodiments, the filter media has an overall thickness ofgreater than or equal to 30 mils and less than or equal to 350 mils.

In certain embodiments, the filter media has an overall thickness ofgreater than or equal to 100 mil and less than or equal to 4000 mil. Incertain embodiments, the filter media has an overall thickness ofgreater than 150 mil and less than or equal to 1000 mil.

In certain embodiments, the filter media has an overall air permeabilityof greater than or equal to 30 CFM and less than or equal to 1100 CFM.In certain embodiments, the filter media has an overall air permeabilityof greater than or equal to 100 CFM and less than or equal to 700 CFM.In certain embodiments, the filter media has an overall air permeabilityof greater than or equal to 10 CFM and less than or equal to 1000 CFM.

In certain embodiments, the filter media has a normalized efficiency ofgreater than or equal to 1 and less than or equal to 3.5.

In certain embodiments, the filter media has a dust holding capacity ofgreater than or equal to about 1 g/m² and less than or equal to about140 g/m². In certain embodiments, the filter media has a dust holdingcapacity of greater than or equal to about 80 g/m² and less than orequal to about 140 g/m².

In certain embodiments, the filter media has a dust holding capacity ofgreater than or equal to 5 g/m² and less than or equal to 600 g/m². Incertain embodiments, the filter media has a dust holding capacity ofgreater than or equal to 200 g/m² and less than or equal to 350 g/m².

In certain embodiments, the filter media has a gamma of greater than orequal to 30 and less than or equal to 250. In certain embodiments, thefilter media has a gamma of greater than or equal to 75 and less than orequal to 150. In certain embodiments, the filter media has a normalizedgamma of greater than or equal to 1 and less than or equal to 10.9. Incertain embodiments, the filter media has a normalized gamma of greaterthan or equal to 1 and less than or equal to 5.6.

In certain embodiments, the filter media has a gamma of greater than orequal to 75 and less than or equal to 150. In certain embodiments, thefilter media has a gamma of greater than or equal to 20 and less than orequal to 250.

In certain embodiments, the filter media has an initial efficiency ofgreater than or equal to 50% and less than or equal to 99.999%. Incertain embodiments, the filter media has an initial efficiency ofgreater than or equal to 90% and less than or equal to 99.999%.

In certain embodiments, the charged fiber layer has a periodicity ofgreater than or equal to 10 and less than or equal to 40 waves per 6inches. In certain embodiments, the charged fiber layer has aperiodicity of greater than or equal to 5 and less than or equal to 9waves per 6 inches. In certain embodiments, the charged fiber layer hasa periodicity of greater than or equal to 3 and less than or equal to 15waves per 6 inches.

In certain embodiments, the filter media comprises a coarse supportlayer. In certain embodiments, the coarse support layer comprises aplurality of fibers having an average fiber diameter of greater than orequal to 8 micron and less than or equal to 85 microns. In certainembodiments, the coarse support layer comprises a plurality of fibershaving an average fiber diameter of greater than or equal to 12 micronsand less than or equal to 60 microns. In certain embodiments, the coarsesupport layer has a basis weight of less than or equal to 100 g/m² andgreater than or equal to 5 g/m². In certain embodiments, the coarsesupport layer has a basis weight of less than or equal to 40 g/m² andgreater than or equal to 12 g/m².

In certain embodiments, the filter media comprises an outer layer.

Other advantages and novel features of the present invention will becomeapparent from the following detailed description of various non-limitingembodiments of the invention when considered in conjunction with theaccompanying figures. In cases where the present specification and adocument incorporated by reference include conflicting and/orinconsistent disclosure, the present specification shall control. If twoor more documents incorporated by reference include conflicting and/orinconsistent disclosure with respect to each other, then the documenthaving the later effective date shall control.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments of the present invention will be described byway of example with reference to the accompanying figures, which areschematic and are not intended to be drawn to scale. In the figures,each identical or nearly identical component illustrated is typicallyrepresented by a single numeral. For purposes of clarity, not everycomponent is labeled in every figure, nor is every component of eachembodiment of the invention shown where illustration is not necessary toallow those of ordinary skill in the art to understand the invention. Inthe figures:

FIG. 1A is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 1B is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 2A is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 2B is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 2C is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 2D is a schematic diagram showing a cross-section of a filter mediaaccording to one set of embodiments;

FIG. 3 is a plot of normalized gamma of exemplary filter media versusbasis weight of a charged fiber layer of the filter media, with orwithout an open support layer, according to one set of embodiments;

FIG. 4 is a plot of normalized efficiency of exemplary filter mediaversus basis weight of a charged fiber layer of the filter media, withor without an open support layer, according to one set of embodiments;

FIG. 5 is a plot of pressure drop (Pa) of exemplary filter media, versusbasis weight of a charged fiber layer, with or without an open supportlayer, according to one set of embodiments; and

FIG. 6 is a plot of air resistance versus dust holding capacity ofexemplary filter media having a basis weight of 70 g/m², each filtermedia comprising a charged fiber with or without an open support layer,according to one set of embodiments.

DETAILED DESCRIPTION

Filter media, such as electret-containing filtration media for filteringgas streams (e.g., air), are described herein. In some embodiments, thefilter media may be designed to have desirable properties such as stablefiltration efficiency over the lifetime of the filter media, increasednormalized gamma, relatively low pressure drop (i.e. resistance), and/orrelatively low basis weight. In certain embodiments, the filter mediamay be a composite of two or more types of fiber layers where each layermay be designed to enhance its function without substantially negativelyimpacting the performance of another layer of the media. For example,one layer of the media may be designed to have a relatively low basisweight and/or a relatively high air permeability, and another layer ofthe media may be designed to have stable filtration efficiency and/or arelatively high efficiency throughout the filter media's lifetime. Thefilter media described herein may be particularly well-suited forapplications that involve filtering gas streams (e.g., face masks, cabinair filtration, vacuum filtration, room filtration, furnace filtration,respirator equipment, residential or industrial HVAC filtration,high-efficiency particulate arrestance (HEPA) filters, ultra-lowparticular air (ULPA) filters, medical equipment), though the media mayalso be used in other applications.

In some embodiments, the filter media described herein may include anopen support layer and a second layer that is charged (e.g., afiltration layer). In certain embodiments described herein, the opensupport layer is mechanically attached (e.g., needled) to the secondlayer. In some embodiments, the open support layer and/or the secondlayer may be in a waved configuration. In some such embodiments, thefilter media may comprise one or more coarse support layers. In certainembodiments, the second layer is in a waved configuration and the one ormore coarse support layers holds the second layer in the wavedconfiguration and maintains separation of peaks and troughs of adjacentwaves of the second layer.

In some cases, the open support layer may be positioned upstream of thecharged fiber layer (e.g., in a filter element) with respect to thedirection of gas/fluid flow. In an alternative set of embodiments, thesecond layer may be positioned upstream of the first layer (e.g., in afilter element) with respect to the direction of gas/fluid flow. Such aconfiguration of layers may also stabilize the filtration efficiency ofthe filter media throughout its lifetime. In some embodiments, thepresence of charges in the second layer may improve the efficiency ofthe media relative to a filter media without charges in the secondlayer.

Advantageously, the open support layer may have a relatively high airpermeability, a relatively low basis weight, and/or a relatively highopen area, thereby providing mechanical reinforcement while adding arelatively small amount of basis weight to the overall filter media(e.g., as compared to filter media including other support layers suchas coarse support layers).

An example of a filter media including two or more layers is shown inFIG. 1A. As shown illustratively in FIG. 1A, a filter media 100, shownin cross section, may include a first layer 110 (e.g., an open supportlayer) and a second layer 120 adjacent first layer 110. In some cases,first layer 110 may be directly adjacent (i.e., in direct contact withat least a portion of) second layer 120. In alternative embodiments,second layer 120 may be positioned upstream or downstream of, but not incontact with, first layer 110. In some embodiments, the first layer isan open support layer, for example, having a relatively high airpermeability and the second layer is a charged fiber layer (e.g., anelectret layer). Other configurations are also possible. For example, insome cases, the filter media includes one or more coarse support layersas described in more detail below.

In some embodiments, the open support layer may be positioned betweentwo layers. For example, as shown illustratively in FIG. 1B, a filtermedia 102, shown in cross section, may include a first layer 110 (e.g.,the open support layer), a second layer 120 adjacent first layer 110,and a third layer 122 adjacent first layer 110. In some cases, firstlayer 110 may be directly adjacent (i.e., in direct contact with atleast a portion of) second layer 120 and/or third layer 122 (e.g., suchthat first layer 110 is disposed between the second layer and the thirdlayer). In alternative embodiments, second layer 120 may be positionedupstream of, but not in contact with, first layer 110, and third layer122 may be position downstream of, but not in contact with, first layer110. In alternative embodiments, second layer 120 may be positioneddownstream of, but not in contact with, first layer 110, and third layer122 may be position upstream of, but not in contact with, first layer110. In some embodiments, the first layer is an open support layer, forexample, having a relatively high air permeability and the second layerand the third layer may each be a charged fiber layer. In alternativeembodiments, the second layer and the third layer may be different. Forexample, in certain embodiments, the first layer is an open supportlayer, the second layer is a charged fiber layer, and the third layer isa coarse support layer. Moreover, while the coarse support layer (e.g.,the third layer) is illustrated as being adjacent the first layer inFIG. 1B, those skilled in the art would understand, based upon theteachings of this specification, that the coarse support layer may beadjacent the second layer or disposed between the first layer and thesecond layer.

The terms “first layer” and “second layer” as used herein generallyrefer to different layers of a filter media and do not necessarilydenote a particular order of the layers (e.g., within a filter element).For example, while in some embodiments a first layer (e.g., an opensupport layer) may be positioned upstream of the second layer withrespect to the direction of fluid flow, in other embodiments the firstlayer may be positioned downstream of the second layer with respect tothe direction of fluid flow. As used herein, when a layer is referred toas being “adjacent” another layer, it can be directly adjacent to thelayer, or one or more intervening layers also may be present. A layerthat is “directly adjacent” another layer means that no interveninglayer is present.

As described above, in some embodiments, the filter media may be anelectret-containing media. For instance, a layer (e.g., a second layer)of the media may be charged. In general, the net charge of the layer(e.g., the second layer) may be negative or positive. In some instances,at least a surface of the second layer may comprise a negatively chargedmaterial and/or a positively charged material. In some embodiments, thepolymers in the second layer (e.g., the first polymer and the secondpolymer) may be selected based on their dielectric constant and/orposition on the triboelectric series, as described herein. For example,in some embodiments the second layer is formed via a carding process(e.g., where the fibers are manipulated by rollers and extensions (e.g.,hooks, needles)). The polymer fibers within the second layer with asignificant difference in dielectric constant and/or that are relativelyfar apart on the triboelectric series may undergo contactelectrification as a result of the carding process to produce a chargednon-woven web. Charged non-woven webs may have enhanced performanceproperties, including an increased efficiency, compared to a similarnon-woven web that is uncharged, all other factors being equal.

In other embodiments, a layer may be neutral (e.g., have no net charge).

As described above and herein, in some embodiments, the filter mediacomprises an open support layer having a relatively high airpermeability and/or a relatively low basis weight. Non-limiting examplesof suitable open support layers include meshes, scrims, and netting. Ina particular set of embodiments, the open support layer is a mesh (e.g.,a mesh having an air permeability greater than 1100 CFM). In anotherparticular set of embodiments, the open support layer is a scrim (e.g.,a scrim having an air permeability greater than 1100 CFM). In someembodiments, the scrim is formed via a meltblown process or a spunbondprocess.

The open support layer, as described herein, may have certain desirablecharacteristics, such as basis weight, solidity, and/or airpermeability. For instance, in some instances, the open support layermay have a basis weight of less than or equal to 200 g/m², less than orequal to 100 g/m², less than or equal to 90 g/m², less than or equal to85 g/m², less than or equal to 80 g/m², less than or equal to 70 g/m²,less than or equal to 60 g/m², less than or equal to 50 g/m², less thanor equal to 40 g/m², less than or equal to 30 g/m², less than or equalto 25 g/m², less than or equal to 10 g/m², or less than or equal to 3g/m². In some embodiments, the open support layer (e.g., a mesh) mayhave a basis weight of greater than or equal to 2 g/m², greater than orequal to 3 g/m², greater than or equal to 10 g/m², greater than or equalto 25 g/m², greater than or equal to 30 g/m², greater than or equal to40 g/m², greater than or equal to 50 g/m², greater than or equal to 60g/m², greater than or equal to 70 g/m², greater than or equal to 80g/m², greater than 85 g/m², greater than or equal to 90 g/m², greaterthan or equal to 100 g/m², or greater than or equal to 200 g/m².Combinations of the above-referenced ranges are also possible (e.g., abasis weight of less than or equal to 200 g/m² and greater than or equalto 2 g/m², a basis weight of less than or equal to 50 g/m² and greaterthan or equal to 5 g/m²). Other values of basis weight are alsopossible. The basis weight may be determined according to test standardASTM D-846.

In certain embodiments, the open support layer has a relatively high airpermeability. For instance, in some embodiments, the open support layer(e.g., a mesh) has an air permeability of greater than 1,100 CFM,greater than or equal to 1,250 CFM, greater than or equal to 1,500 CFM,greater than or equal to 1,750 CFM, greater than or equal to 2,000 CFM,greater than or equal to 2,500 CFM, greater than or equal to 3,000 CFM,greater than or equal to 5,000 CFM, greater than or equal to 7,500 CFM,greater than or equal to 10,000 CFM, greater than or equal to 12,500CFM, greater than or equal to 15,000 CFM, or greater than or equal to17,500 CFM. In some embodiments, the open support layer has an airpermeability of less than or equal to 20,000 CFM, less than or equal to17,500 CFM, less than or equal to 15,000 CFM, less than or equal to12,500 CFM, less than or equal to 10,000 CFM, less than or equal to7,500 CFM, less than or equal to 5,000 CFM, less than or equal to 3,000CFM, less than or equal to 2,500 CFM, less than or equal to 2,000 CFM,less than or equal to 1,750 CFM, less than or equal to 1,500 CFM, orless than or equal to 1,250 CFM. Combinations of the above-referencedranges are also possible (e.g., an air permeability of greater than1,100 CFM and less than or equal to 20,000 CFM). Other values of airpermeability are also possible. Air permeability of the open supportlayer, as determined herein, is measured according to the test standardASTM D737 over 38 cm² surface area of the media and using a pressure of125 Pa.

In certain embodiments, the open support layer may have a solidity ofless than or equal to 10%, less than or equal to 8%, less than or equalto 6%, less than or equal to 5%, less than or equal to 4%, less than orequal to 3%, less than or equal to 2%, less than or equal to 1%, or lessthan or equal to 0.5%. In some embodiments, the open support layer mayhave a solidity of greater than or equal to 0.1%, greater than or equalto 0.5%, greater than or equal to 1%, greater than or equal to 2%,greater than or equal to 3%, greater than or equal to 4%, greater thanor equal to 5%, greater than or equal to 6%, or greater than or equal to8%. Combinations of the above-referenced ranges are also possible (e.g.,a solidity of less than or equal to 10% and greater than or equal to0.1%, less than or equal to 2% and greater than or equal to 0.1%). Otherranges are also possible. Solidity generally refers to the percentage ofvolume of solids with respect to the total volume of the layer.

The open support layer (e.g., a mesh, a netting) may have, in somecases, a particular strand count. In some embodiments, the strand countmay be greater than or equal to 2 strands per inch, greater than orequal to 3 strands per inch, greater than or equal to 5 strands perinch, greater than or equal to 7 strands per inch, greater than or equalto 10 strands per inch, greater than or equal to 12 strands per inch,greater than or equal to 15 strands per inch, greater than or equal to17 strands per inch, greater than or equal to 20 strands per inch,greater than or equal to 22 strands per inch, or greater than or equalto 25 strands per inch. In certain embodiments, the strand count may beless than or equal to 27 strands per inch, less than or equal to 25strands per inch, less than or equal to 22 strands per inch, less thanor equal to 20 strands per inch, less than or equal to 17 strands perinch, less than or equal to 15 strands per inch, less than or equal to12 strands per inch, less than or equal to 10 strands per inch, lessthan or equal to 7 strands per inch, less than or equal to 5 strands perinch, or less than or equal to 3 strands per inch. Combinations of theabove-referenced ranges are also possible (e.g., a strand count ofgreater than or equal to 2 strands per inch and less than or equal to 27strands per inch, greater than or equal to 3 strands per inch and lessthan or equal to 20 strands per inch). Other ranges of strand count arealso possible. Strand count, as used herein, is measured along a firstaxis of the open support layer. In some embodiments, the open supportlayer (e.g., a mesh) may have a first strand count in a first axis ofthe open support layer, and a second strand count, different than thefirst strand count, in a second axis of the open support layerorthogonal to the first axis. The second strand count measured along asecond axis of the open support layer may range as noted above in thecontext of the strand count measured along a first axis of the opensupport layer (e.g., a second strand count of greater than or equal to 2strands per inch and less than or equal to 27 strands per inch, greaterthan or equal to 3 strands per inch and less than or equal to 20 strandsper inch). The term axis, as used herein, generally refers to areference direction of the layer parallel to one or more strands in thelayer. For example, strand count may be determined by counting thenumber of strands per inch laying substantially perpendicular to theparticular axis (e.g., the number of strands/fibers intersecting thestrand parallel to the axis). In some embodiments, the open supportlayer comprises a plurality of fibers or strands. The fibers or strandsof the open support layer may be continuous or non-continuous.Continuous fibers (e.g., strands) and are made by a “continuous”fiber-forming process, such as a meltblown process, a meltspun, anextrusion process, woven yarns, laid scrims, and/or a spunbond process,and typically have longer lengths than non-continuous fibers asdescribed in more detail below. Non-continuous fibers are, for example,staple fibers that are generally cut (e.g., from a filament) or formedas non-continuous discrete fibers to have a particular length or a rangeof lengths as described in more detail below.

In certain embodiments, the plurality of fibers or strands of the opensupport layer include synthetic fibers or strands (e.g., syntheticpolymer fibers or strands). The synthetic fibers or strands of the opensupport layer may be continuous fibers. Non-limiting examples ofsuitable synthetic fibers/strands include polyester, polyaramid,polyimide, polyolefin (e.g., polyethylene such as high densitypolyethylene, low density polyethylene, and/or linear low densitypolyethylene), ethylene-vinyl acetate, polyacrylamide, polylactic acid,polypropylene, Kevlar, Nomex, halogenated polymers (e.g., polyethyleneterephthalate), acrylics, polyphenylene oxide, polyphenylene sulfide,thermoplastic elastomers (e.g., thermoplastic polyurethane), andcombinations thereof.

Other processes and materials used to form the open support layer arealso possible. For example, in some embodiments, the open support layeris a fibrous layer, an extruded layer, an oriented layer, a woven layer,or a non-woven layer.

In certain embodiments, an adhesive is co-extruded with one or morefibers/strands of the open support layer (e.g., for joining the opensupport layer to a second layer).

In some embodiments, the plurality of fibers (or strands) in the opensupport layer may have an average fiber (or strand) diameter of greaterthan or equal to 0.5 microns, greater than or equal to 1 micron, greaterthan or equal to 2 microns, greater than or equal to 3 microns, greaterthan or equal to 4 microns, greater than or equal to 5 microns, greaterthan or equal to 6 microns, greater than or equal to 8 microns, greaterthan or equal to 10 microns, greater than or equal to 15 microns,greater than or equal to 20 microns, greater than or equal to 50microns, greater than or equal to 75 microns, greater than or equal to100 microns, greater than or equal to 250 microns, greater than or equalto 500 microns, greater than or equal to 750 microns, greater than orequal to 1 mm, greater than or equal to 1.25 mm, greater than or equalto 1.5 mm, or greater than or equal to 1.75 mm. In some embodiments, theplurality of fibers in the open support layer may have an average fiber(or strand) diameter of less than or equal to 2 mm, less than or equalto 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm,less than or equal to 1 mm, less than or equal to 750 microns, less thanor equal to 500 microns, less than or equal to 250 microns, less than orequal to 100 microns, less than or equal to 75 microns, less than orequal to 50 microns, less than or equal to 20 microns, less than orequal to 15 microns, less than or equal to 10 microns, less than orequal to 8 microns, less than or equal to 7 microns, less than or equalto 6 microns, less than or equal to 5 microns, less than or equal to 4microns, less than or equal to 3 microns, less than or equal to 2microns, or less than or equal to 1 micron. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 0.5 microns and less than or equal to 2 mm, greater than or equal to0.5 microns and less than or equal to 10 microns, greater than or equalto 10 microns and less than or equal 20 microns, greater than or equalto 500 microns and less than or equal to 2 mm). Other values of averagefiber (or strand) diameter for the open support layer are also possible.Individual fiber/strand diameters within the open support layer may bemeasured by microscopy, for example scanning electron microscopy (SEM),and statistics regarding fiber/strand diameter such as averagefiber/strand diameter, median fiber/strand diameter, and fiber/stranddiameter standard deviation may be determined by performing appropriatestatistical techniques on the measured fiber/strand diameters.

In an exemplary embodiment, the open support layer is formed by aspunbond process and comprises a plurality of fibers having an averagefiber diameter of greater than or equal to 10 microns and less than orequal to 20 microns, In another exemplary embodiment, the open supportlayer is formed by a meltblown process and comprises a plurality offibers having an average fiber diameter of greater than or equal to 0.5microns and less than or equal to 10 microns. In yet another exemplaryembodiment, the open support layer is a mesh and comprises a pluralityof strands having an average strand diameter of greater than or equal to500 microns and less than or equal to 2 mm.

In some embodiments, the open support layer comprises a plurality offibers (e.g., synthetic fibers, continuous fibers) (or strands) having acontinuous length. In certain embodiments, the plurality of fibers (orstrands) in the open support layer may have an average length of greaterthan about 5 inches, greater than or equal to 10 inches, greater than orequal to 25 inches, greater than or equal to 50 inches, greater than orequal to 100 inches, greater than or equal to 300 inches, greater thanor equal to 500 inches, greater than or equal to 700 inches, or greaterthan or equal to 900 inches. In some instances, the fibers (or strands)may have an average length of less than or equal to 1000 inches, lessthan or equal to 800 inches, less than or equal to 600 inches, less thanor equal to 400 inches, or less than or equal to 100 inches.Combinations of the above-referenced ranges are also possible (e.g.,greater than or equal to 50 inches and less than or equal to 1000inches). Other ranges are also possible.

In other embodiments, the open support layer comprises a plurality offibers (e.g., synthetic fibers, staple fibers) (or strands) having anaverage length of less than about 5 inches (127 mm). For example, theplurality of fibers (or strands) in the open support layer may have anaverage length of, for example, less than or equal to 100 mm, less thanor equal to 80 mm, less than or equal to 60 mm, less than or equal to 40mm, less than or equal to 20 mm, less than or equal to 10 mm, less thanor equal to 5 mm, less than or equal to 1 mm, less than or equal to 0.5mm, or less than or equal to 0.1 mm. In some instances, plurality offibers (or strands) in the open support layer may have an average lengthof greater than or equal to 0.02 mm, greater than or equal to 0.1 mm,greater than or equal to 0.5 mm, greater than or equal to 1 mm, greaterthan or equal to 5 mm, greater than or equal to 10 mm, greater than orequal to 20 mm, greater than or equal to 40 mm, greater than or equal to60 mm. Combinations of the above-referenced ranges are possible (e.g.,greater than or equal to 0.02 mm and less than or equal to 80 mm,greater than or equal to 0.03 mm and less than or equal to 40 mm). Otherranges are also possible.

In some embodiments, the open support layer has a dry tensile strengthof greater than or equal 4 lbs/in, greater than or equal to 5 lbs/in,greater than or equal to 7 lbs/in, greater than or equal to 10 lbs/in,greater than or equal to 15 lbs/in, greater than or equal to 20 lbs/in,greater than or equal to 25 lbs/in, greater than or equal to 30 lbs/in,greater than or equal to 35 lbs/in, greater than or equal to 40 lbs/in,greater than or equal to 45 lbs/in, greater than or equal to 50 lbs/in,or greater than or equal to 55 lbs/in. In certain embodiments, the opensupport layer has a dry tensile strength of less than or equal to 60lbs/in, less than or equal to 55 lbs/in, less than or equal to 50lbs/in, less than or equal to 45 lbs/in, less than or equal to 40lbs/in, less than or equal to 35 lbs/in, less than or equal to 30lbs/in, less than or equal to 25 lbs/in, less than or equal to 20lbs/in, less than or equal to 15 lbs/in, less than or equal to 10lbs/in, less than or equal to 7 lbs/in, or less than or equal to 5lbs/in. Combinations of the above-referenced ranges are also possible(e.g., a dry tensile strength of greater than or equal to 4 lbs/in andless than or equal to 60 lbs/in, greater than or equal to 10 lbs/in andless than or equal to 30 lbs/in). Other ranges are also possible. Asdetermined herein, the dry tensile strength is measured according to thestandard EN/ISO 1924-4 using a jaw separation speed of 10 mm/min and asample size of 3 inches by 6 inches.

In some cases, the open support layer may have a particular thickness.For example, in some embodiments, the thickness is greater than or equalto 10 microns, greater than or equal to 15 microns, greater than orequal to 20 microns, greater than or equal to 50 microns, greater thanor equal to 75 microns, greater than or equal to 100 microns, greaterthan or equal to 250 microns, greater than or equal to 500 microns,greater than or equal to 750 microns, greater than or equal to 1 mm,greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, orgreater than or equal to 1.75 mm. In some embodiments, the thickness ofthe open support layer may be less than or equal to 2 mm, less than orequal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to1.25 mm, less than or equal to 1 mm, less than or equal to 750 microns,less than or equal to 500 microns, less than or equal to 250 microns,less than or equal to 100 microns, less than or equal to 75 microns,less than or equal to 50 microns, less than or equal to 20 microns, orless than or equal to 15 microns. Combinations of the above referencedranges are also possible (e.g., a thickness of greater than or equal to10 microns and less than or equal to 2 mm, greater than or equal to 250microns and less than or equal to 2 mm). Other ranges are also possible.Thickness, as determined herein, may be measured according to ASTMstandard D-1777 at 0.3 psi.

In certain embodiments, the open support layer may have a dry tensileelongation at break of greater than or equal to 5%. For example, in someembodiments, the open support layer may have a dry tensile elongation atbreak of greater than or equal to 5%, greater than or equal to 10%,greater than or equal to 20%, greater than or equal to 30%, greater thanor equal to 40%, greater than or equal to 50%, greater than or equal to60%, greater than or equal to 70%, greater than or equal to 80%, greaterthan or equal to 90%, greater than or equal to 100%, greater than orequal to 110%, greater than or equal to 120%, greater than equal to130%, or greater than or equal to 140%. In certain embodiments, the opensupport layer may have a dry tensile elongation at break of less than orequal to 150%, less than or equal to 140%, less than or equal to 130%,less than or equal to 120%, less than or equal to 110%, less than orequal to 100%, less than or equal to 90%, less than or 80%, less than orequal to 70%, less than or equal to 60%, less than or equal to 50%, lessthan or equal to 40%, less than or equal to 30%, less than or equal to20%, or less than or equal to 10%. Combinations of the above referenceranges are also possible (e.g., greater than or equal to 5% and lessthan or equal to 150%, greater than or equal to 10% and less than orequal to 60%). Other ranges are also possible. As determined herein, thedry tensile elongation at break is measured according to the standardEN/ISO 1924-4 using a jaw separation speed of 10 mm/min.

The first layer (e.g., an open support layer such as a mesh) and thesecond layer (e.g., a charged fiber layer) may be joined to one another(e.g., by mechanical attachment, lamination, point bonding, thermo-dotbonding, ultrasonic bonding, calendering, use of adhesives (e.g.,glue-web), and/or co-pleating). In some embodiments, the first layer(e.g., the open support layer) and the second layer may be mechanicallyattached. Non-limiting examples of suitable means for mechanicalattachment include needling, stitching, and hydroentangling. In aparticular set of embodiments, the first layer is needled to the secondlayer. In certain embodiments, the first layer and the second layer maybe mechanically attached to one another such that the filter mediacomprising the first layer and the second layer is substantially free ofadhesives. For example, in some embodiments, an open support layer ismechanically attached to the second layer (e.g., a charged fiber layer)and are joined to one another without an adhesive. In alternativeembodiments, the open support layer and the second layer may be joinedto one another by mechanical attachment and an adhesive.

In embodiments in which a first layer (e.g., an open support layer suchas a mesh) is needled to a second layer (e.g., a charged fiber layer),the needling may have a particular punch density. In some embodiments,the punch density of needling is greater than or equal to 15 punches persquare centimeter, greater than or equal to 20 punches per squarecentimeter, greater than or equal to 25 punches per square centimeter,greater than or equal to 30 punches per square centimeter, greater thanor equal to 35 punches per square centimeter, greater than or equal to40 punches per square centimeter, greater than or equal to 45 punchesper square centimeter, greater than or equal to 50 punches per squarecentimeter, or greater than or equal to 55 punches per squarecentimeter. In certain embodiments, the needling punch density is lessthan or equal to 60 punches per square centimeter, less than or equal to55 punches per square centimeter, less than or equal to 50 punches persquare centimeter, less than or equal to 45 punches per squarecentimeter, less than or equal to 40 punches per square centimeter, lessthan or equal to 35 punches per square centimeter, less than or equal to30 punches per square centimeter, less than or equal to 25 punches persquare centimeter, or less than or equal to 20 punches per squarecentimeter. Combinations of the above referenced ranges are alsopossible (e.g., greater than or equal to 15 punches per squarecentimeter and less than or equal to 60 punches per square centimeter,greater than or equal to 25 punches per square centimeter and less thanor equal to 45 punches per square centimeter). Other ranges are alsopossible.

The open support layer may be needled to the charged fiber layer using aparticular penetration depth of needling across at least the two layers.In certain embodiments, the penetration depth of needling across two ormore layers of the filter media (e.g., an open support layer and acharged fiber layer) is greater than or equal to 8 mm, greater than orequal to 10 mm, greater than or equal to 12 mm, greater than or equal to14 mm, greater than or equal to 16 mm, or greater than or equal to 18mm. In certain embodiments, the penetration depth of needling across twoor more layers of the filter media is less than or equal to 20 mm, lessthan or equal to 18 mm, less than or equal to 16 mm, less than or equalto 14 mm, less than or equal to 12 mm, or less than or equal to 10 mm.Combinations of the above referenced ranges are also possible (e.g., apenetration depth of needling of greater than or equal to 8 mm and lessthan or equal to 20 mm, greater than or equal to 12 mm and less than orequal to 16 mm). Other ranges are also possible.

As described above and herein, in some embodiments, the second layer isa charged fiber layer. In certain embodiments, the charged fiber layercomprises a plurality of fibers. The fibers of the second layer may benon-continuous (e.g., staple fibers).

The charged fiber layer, as described herein, may have certainstructural characteristics, such as basis weight and/or fiber diameter.For instance, in some embodiments, the charged fiber layer may have abasis weight of greater than or equal to 12 g/m², greater than or equalto 15 g/m², greater than or equal to 20 g/m², greater than or equal to25 g/m², greater than or equal to 30 g/m², greater than or equal to 40g/m², greater than or equal to 50 g/m², greater than or equal to 60g/m², greater than or equal to 70 g/m², greater than or equal to 80g/m², greater than or equal to 100 g/m², greater than or equal to 200g/m², greater than or equal to 300 g/m², greater than or equal to 400g/m², greater than or equal to 500 g/m², or greater than or equal to 600g/m². In some instances, the charged fiber layer may have a basis weightof less than or equal to 700 g/m², less than or equal to 600 g/m², lessthan or equal to 500 g/m², less than or equal to 400 g/m², less than orequal to 300 g/m², less than or equal to 200 g/m², less than or equal to100 g/m², less than or equal to 90 g/m², less than or equal to 80 g/m²,less than or equal to 70 g/m², less than or equal to 60 g/m², less thanor equal to 50 g/m², less than or equal to 40 g/m², less than or equalto 30 g/m², less than or equal to 25 g/m², less than or equal to 20g/m², or less than or equal to 15 g/m². Combinations of theabove-referenced ranges are also possible (e.g., a basis weight ofgreater than or equal to 12 g/m² and less than or equal to 700 g/m², abasis weight of greater than or equal to 12 g/m² and less than or equalto 250 g/m², a basis weight of greater than or equal to 15 g/m² and lessthan or equal to 100 g/m²). Other values of basis weight are alsopossible. The basis weight may be determined as described above.

In some embodiments, the charged fiber layer may comprise a plurality offibers having a particular average fiber diameter. In some embodiments,the plurality of fibers of the second layer have an average fiberdiameter of greater than or equal to 1 micron, greater than or equal to2 microns, greater than or equal to 3 microns, greater than or equal to5 microns, greater than or equal to 7 microns, greater than or equal to9 microns, greater than or equal to 10 microns, greater than or equal to12 microns, greater than or equal to 14 microns, greater than or equalto 15 microns, greater than or equal to 16 microns, greater than orequal to 18 microns, greater than or equal to 19 microns, greater thanor equal to 20 microns, or greater than or equal to 21 microns. Incertain embodiments, the plurality of fibers of the second layer have anaverage fiber diameter of less than or equal to 22 microns, less than orequal to 21 microns, less than or equal to 20 microns, less than orequal to 19 microns, less than or equal to 18 microns, less than orequal to 16 microns, less than or equal to 15 microns, less than orequal to 14 microns, less than or equal to 12 microns, less than orequal to 10 microns, less than or equal to 9 microns, less than or equalto 7 microns, less than or equal to 5 microns, less than or equal to 4microns, less than or equal to 3 microns, or less than or equal to 2microns. Combinations of the above-referenced ranges are also possible(e.g., an average fiber diameter of greater than or equal to 1 micronand less than or equal to 22 microns, greater than or equal to 1 micronand less than or equal to 15 microns, greater than or equal to 15microns and less than or equal to 22 microns). Other ranges alsopossible.

In some embodiments, the charged fiber layer may comprise a plurality offibers that are relatively fine (e.g., having an average fiber diameterless than 15 microns). For example, in certain embodiments, the secondlayer comprises a plurality of fibers having an average fiber diameterless than 15 microns, less than or equal to 14 microns, less than orequal to 12 microns, less than or equal to 10 microns, less than orequal to 9 microns, less than or equal to 7 microns, less than or equalto 5 microns, less than or equal to 4 microns, less than or equal to 3microns, or less than or equal to 2 microns. In some embodiments, thesecond layer comprises a plurality of fibers having an average fiberdiameter of greater than or equal to 1 micron, greater than or equal to2 microns, greater than or equal to 3 microns, greater than or equal to5 microns, greater than or equal to 7 microns, greater than or equal to9 microns, greater than or equal to 10 microns, greater than or equal to12 microns, or greater than or equal to 14 microns. Combinations of theabove-referenced ranges are also possible (e.g., less than 15 micronsand greater than or equal to 1 micron, less than 15 microns and greaterthan or equal to 3 microns, less than or equal to 12 microns and greaterthan or equal to 3 microns). Other ranges are also possible. In anexemplary embodiment, the filter media comprises an open support layer(i.e. a first layer) and a charged fiber layer (i.e. a second layer)adjacent the open support layer, the charged fiber layer comprising aplurality of fibers having an average fiber diameter less than 15microns.

In some embodiments, as described herein, the charged fiber layer maycomprise a one or more plurality of fibers. For example, in certainembodiments, the charged fiber layer comprises a first plurality offibers (e.g., comprising a first polymer) and a second plurality offibers (e.g., comprising a second polymer, different than the firstpolymer). In some such embodiments, each of the plurality of fibers(e.g., the first plurality of fibers, the second plurality of fibers)may have an average fiber diameter as described above. For example, inan exemplary embodiment, the charged fiber layer comprises a firstplurality of fibers and a second plurality of fibers, the firstplurality of fibers and/or the second plurality of fibers having anaverage fiber diameter of less than 15 microns and greater than or equalto 1 micron. In another exemplary embodiment, the charged fiber layercomprises a first plurality of fibers and a second plurality of fibers,the first plurality of fibers and/or the second plurality of fibershaving an average fiber diameter of greater than or equal to 1 micronand less than or equal to 22 microns.

In certain embodiments, the plurality of fibers of the charged fiberlayer include synthetic fibers (synthetic polymer fibers). The syntheticfibers of the second layer may be staple fibers. Non-limiting examplesof suitable synthetic fibers include polypropylene, dry-spun acrylic(e.g., produced from a dry-spinning process), polyvinyl chloride,mod-acrylic, wet spun acrylic, polytetrafluoroethylene, polypropylene,polystyrene, polysulfone, polyethersulfone, polycarbonate, nylon (e.g.,nylon 6/6), polyurethane, phenolic, polyvinylidene fluoride, polyester,polyaramid, polyimide, polyolefin (e.g., polyethylene), Kevlar, Nomex,halogenated polymers (e.g., polyethylene terephthalate), polyacrylics,polyphenylene oxide, polyphenylene sulfide, and combinations thereof. Insome embodiments, the synthetic fibers are halogen-free such thatsignificant dioxins are not detectable when incinerated. For example,the fibers may be halogen-free acrylic fibers formed by dry spinning. Insome embodiments, the second layer and/or the entire filter media ishalogen-free such that significant dioxins are not detectable whenincinerated.

In some embodiments, the charged fiber layer comprises a mixture of twoor more polymeric fibers. For instance, the charged fiber layer maycomprise at least a first plurality of fibers comprising a first polymerand a second plurality of fibers comprising a second polymer. Forexample, in an exemplary embodiment, the charged fiber layer comprises afirst plurality of fibers comprising a first polymer where the firstpolymer is acrylic (e.g., dry-spun acrylic). In certain embodiments, thecharged fiber layer comprises a second plurality of fibers comprising asecond type of polymer fiber, different than the first type of polymerfiber. In certain embodiments, the second type of polymer fiber ispolypropylene.

In certain embodiments, the first polymer and the second polymer areselected such that the first polymer and the second polymer havedifferent dielectric constants. The two polymers having differentdielectric constants may facilitate charging of the layer (e.g.,triboelectric charging). Without wishing to be bound by theory, twopolymers with different dielectric constants in the layer may come intofrictional contact during manufacture of the layer such that one polymerwill lose electrons and give them away to the other polymer and, as aresult, the polymer losing electrons is net positively charged, theother polymer receiving electrons is net negatively charged. Inembodiments in which the second layer of the filter media is a chargedfiber layer, the charged layer may have one or more characteristicsdescribed in commonly-owned U.S. Pat. No. 6,623,548, entitled “Filtermaterials and methods for the production thereof”, issued Sep. 23, 2003,which is incorporated herein by reference in its entirety for allpurposes. For example, in some embodiments, the second layer is anelectrostatically charged layer formed by blending togetherpolypropylene fibers with halogen free acrylic fibers, polypropylenewith polyvinyl chloride (PVC) fibers, or a mixture of halogen freeacrylic fibers and PVC fibers and, optionally, carding the blendedfibers so as to form a non-woven fabric.

In some embodiments, the difference in dielectric constants between thefirst polymer and the second polymer may be selected to be greater thanor equal to 0.8, greater than or equal to 1, greater than or equal to1.2, greater than or equal to 1.5, greater than or equal to 2, greaterthan or equal to 3, greater than or equal to 5, or greater than or equalto 7. In certain embodiments, the difference in dielectric constantsbetween the first polymer and the second polymer may be selected to beless than or equal to 8, less than or equal to 7, less than or equal to5, less than or equal to 3, less than or equal to 2, less than or equalto 1.5, less than or equal to 1.2, or less than or equal to 1.Combinations of the above-referenced ranges are also possible (e.g., thedifference in dielectric constants between the first polymer and thesecond polymer is greater than or equal to 0.8 and less than or equal to8, greater than or equal to 1.5 and less than or equal to 5). Otherranges are also possible.

Table 1 shows representative dielectric constants for several exemplarypolymers.

TABLE 1 Materials Dielectric constant Polytetrafluoroethylene 2.10Polypropylene  2.2-2.36 Polyethylene 2.25-2.35 Polystyrene 2.45-2.65Polyvinyl chloride 2.8-3.1 Polysulfone 3.07 Polyethersulfone 3.10Polyethylene terephthalate 3.1 Polycarbonate 3.17 Acrylic 3.5-4.5 Nylon6/6 4.0-4.6 Polyurethane 6.3 Phenolic 6.5 Polyvinylidene fluoride 8.4

The first polymer and the second polymer may be present in the secondlayer in any suitable amount. For example, in some embodiments, thefirst polymer is present in the second layer in an amount of greaterthan or equal to 10 wt %, greater than or equal to 15 wt %, greater thanor equal to 20 wt %, greater than or equal to 25 wt %, greater than orequal to 30 wt %, greater than or equal to 35 wt %, greater than orequal to 40 wt %, greater than or equal to 50 wt %, greater than orequal to 60 wt %, greater than or equal to 65 wt %, greater than orequal to 70 wt %, greater than or equal to 75 wt %, greater than orequal to 80 wt %, or greater than or equal to 85 wt % with respect tothe total amount of fibers in the layer and/or the total weight of thelayer. In certain embodiments, the first polymer is present in thesecond layer in an amount of less than or equal to 90 wt %, less than orequal to 85 wt %, less than or equal to 80 wt %, less than or equal to75 wt %, less than or equal to 70 wt %, less than or equal to 65 wt %,less than or equal to 60 wt %, less than or equal to 50 wt %, less thanor equal to 40 wt %, less than or equal to 35 wt %, less than or equalto 30 wt %, less than or equal to 25 wt %, less than or equal to 20 wt%, or less than or equal to 15 wt % with respect to the total amount offibers in the layer and/or the total weight of the layer. Combinationsof the above referenced ranges are also possible (e.g., greater than orequal to 10 wt % and less than or equal to 90 wt %, greater than orequal to 25 wt % and less than or equal to 75 wt %, greater than orequal to 35 wt % and less than or equal to 65 wt %). Other ranges arealso possible.

In some embodiments, the second polymer is present in the second layerin an amount of less than or equal to 90 wt %, less than or equal to 85wt %, less than or equal to 80 wt %, less than or equal to 75 wt %, lessthan or equal to 70 wt %, less than or equal to 65 wt %, less than orequal to 60 wt %, less than or equal to 50 wt %, less than or equal to40 wt %, less than or equal to 35 wt %, less than or equal to 30 wt %,less than or equal to 25 wt %, less than or equal to 20 wt %, or lessthan or equal to 15 wt % with respect to the total amount of fibers inthe layer and/or the total weight of the layer. In certain embodiments,the second polymer is present in the second layer in an amount ofgreater than or equal to 10 wt %, greater than or equal to 15 wt %,greater than or equal to 20 wt %, greater than or equal to 25 wt %,greater than or equal to 30 wt %, greater than or equal to 35 wt %,greater than or equal to 40 wt %, greater than or equal to 50 wt %,greater than or equal to 60 wt %, greater than or equal to 65 wt %,greater than or equal to 70 wt %, greater than or equal to 75 wt %,greater than or equal to 80 wt %, or greater than or equal to 85 wt %with respect to the total amount of fibers in the layer and/or the totalweight of the layer. Combinations of the above referenced ranges arealso possible (e.g., greater than or equal to 10 wt % and less than orequal to 90 wt %, greater than or equal to 25 wt % and less than orequal to 75 wt %, greater than or equal to 35 wt % and less than orequal to 65 wt %). Other ranges are also possible.

In some embodiments, the second layer comprises the first polymer in anamount of greater than or equal to 10 wt % and less than or equal to 90wt % and the second polymer in an amount of less than or equal to 90 wt% and greater than or equal to 10 wt % with respect to the total amountof fibers in the layer. For example, in some embodiments, the secondlayer comprises the first polymer in an amount of greater than or equalto 25 wt % and less than or equal to 75 wt % and the second polymer inan amount of less than or equal to 75 wt % and greater than or equal to25 wt % with respect to the total amount of fibers in the layer. Incertain embodiments, the second layer may comprise the first polymer inan amount of greater than or equal to 35 wt % and less than or equal to65 wt %, and the second polymer in an amount of less than or equal to 65wt % and greater than or equal to 35 wt %, with respect to the totalamount of fibers in the layer. In certain embodiments, the second layercomprises each of the first polymer and the second polymer in an amountof about 50 wt % with respect to the total amount of fibers in thelayer.

In some embodiments, the charged fiber layer comprises a plurality offibers (e.g., synthetic fibers, staple fibers) having an average lengthof less than 5 inches (127 mm). For example, the plurality of fibers inthe charged fiber layer may have an average length of, for example, lessthan or equal to 100 mm, less than or equal to 80 mm, less than or equalto 60 mm, less than or equal to 40 mm, less than or equal to 20 mm, lessthan or equal to 10 mm, less than or equal to 5 mm, less than or equalto 1 mm, less than or equal to 0.5 mm, or less than or equal to 0.1 mm.In some instances, plurality of fibers in the charged fiber layer mayhave an average length of greater than or equal to 0.02 mm, greater thanor equal to 0.1 mm, greater than or equal to 0.5 mm, greater than orequal to 1 mm, greater than or equal to 5 mm, greater than or equal to10 mm, greater than or equal to 20 mm, greater than or equal to 40 mm,greater than or equal to 60 mm. Combinations of the above-referencedranges are possible (e.g., greater than or equal to 1 mm and less thanor equal to 80 mm, greater than or equal to 1 mm and less than or equalto 60 mm). Other ranges are also possible.

In some embodiments, the charged fiber layer may be designed to have aparticular uncompressed thickness. In some embodiments, the uncompressedthickness of the charged fiber layer may be greater than or equal togreater than or equal to 5 mils, greater than or equal to 10 mils,greater than or equal to 25 mils, greater than or equal to 30 mils,greater than or equal to 50 mils, greater than or equal to 100 mils,greater than or equal to 200 mils, greater than or equal to 250 mils,greater than or equal to 300 mils, greater than or equal to 350 mils,greater than or equal to 400 mils, greater than or equal to 450 mils, orgreater than or equal to 500 mils. In certain embodiments, theuncompressed thickness of the charged fiber layer may be less than orequal to 600 mils, less than or equal to 500 mils, less than or equal to450 mils, less than or equal to 400 mils, less than or equal to 350mils, less than or equal to 300 mils, less than or equal to 250 mils,less than or equal to 200 mils, less than or equal to 100 mils, lessthan or equal to 50 mils, less than or equal to 25 mils, or less than orequal to 10 mils. Combinations of the above referenced ranges are alsopossible (e.g., greater than or equal to 5 mils and less than or equalto 600 mils, greater than or equal to 30 mils and less than or equal to350 mils). Other ranges are also possible. Uncompressed thickness, asused herein, is determined using a Mitutoyo thickness gauge. Briefly,the fiber layer is compressed using a circular probe having a diameterof 1 mm under at least three different weights (e.g., 10 grams, 5 grams,2 grams). The ordinary least squares linear regression is determined foreach weight and corresponding thickness, and is used to calculated thethickness of the fiber layer corresponding to 0 grams of applied weight(i.e. the uncompressed thickness for that layer).

In certain embodiments, the charged fiber layer may have a particularair permeability. In some embodiments, the air permeability of thecharged fiber layer is greater than or equal to 10 CFM, greater than orequal to 25 CFM, greater than or equal to 50 CFM, greater than or equalto 80 CFM, greater than or equal to 100 CFM, greater than or equal to200 CFM, greater than or equal to 250 CFM, greater than or equal to 300CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM,greater than or equal to 450 CFM, greater than or equal to 500 CFM,greater than or equal to 550 CFM, greater than or equal to 600 CFM,greater than or equal to 650 CFM, greater than or equal to 700 CFM,greater than or equal to 750 CFM, greater than or equal to 800 CFM,greater than or equal to 850 CFM, greater than or equal to 900 CFM,greater than or equal to 950 CFM, greater than or equal to 1000 CFM,greater than or equal to 1050 CFM, greater than or equal to 1100 CFM, orgreater than or equal to 1150 CFM. In certain embodiments, the airpermeability of the charged fiber layer is less than or equal to 1200CFM, less than or equal to 1150 CFM, less than or equal to 1100 CFM,less than or equal to 1050 CFM, less than or equal to 1000 CFM, lessthan or equal to 950 CFM, less than or equal to 900 CFM, less than orequal to 850 CFM, less than or equal to 800 CFM, less than or equal to750 CFM, less than or equal to 700 CFM, less than or equal to 650 CFM,less than or equal to 600 CFM, less than or equal to 550 CFM, less thanor equal to 500 CFM, less than or equal to 450 CFM, less than or equalto 400 CFM, less than or equal to 350 CFM, less than or equal to 300CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, lessthan or equal to 150 CFM, less than or equal to 100 CFM, less than orequal to 80 CFM, less than or equal to 50 CFM, or less than or equal to25 CFM. Combinations of the above referenced ranges are also possible(e.g., greater than or equal to 10 CFM and less than or equal to 1200CFM, greater than or equal to 80 CFM and less than or equal to 1200 CFM,greater than or equal to 50 CFM and less than or equal to 650 CFM).Other ranges are also possible. Air permeability of the second layer, asused herein, is measured according to the test standard ASTM D737 over38 cm² surface area of the media and using a pressure of 125 Pa.

In some embodiments, the filter media comprises a first layer and asecond layer as described above and herein. For example, in one set ofembodiments, the filter media comprises an open support layer (i.e. thefirst layer) and a charged fiber layer (i.e. the second layer)mechanically attached to the open support layer. Referring again to FIG.1A, in some embodiments, filter media 100 comprises an open supportlayer (i.e. first layer 110) mechanically attached to a charged fiberlayer (i.e. second layer 120). In some such embodiments, the opensupport layer has an air permeability of greater than 1100 CFM and lessthan or equal to 20000 CFM and/or a solidity of less than or equal to10%. In some cases, the open support layer may be a mesh. In someembodiments, the filter media includes an open support layer (e.g., amesh) mechanically attached (e.g., needled) to a charged fiber layercomprising a plurality of fibers having a relatively low fiber diameter.Without wishing to be bound by theory, the incorporation of fibershaving relatively low fiber diameters (e.g., less than 15 microns)increases the surface area of the fiber layer and generally increasesfiltration performance and/or provides a relatively low pressure dropacross the fiber layer.

The filter media may comprise any suitable number of open support layersand/or charged fiber layers, each of which may or may not bemechanically attached to one another. For example, in some embodiments,the filter media may comprise a charged fiber layer disposed between twoopen support layers (e.g., a first open support layer upstream andmechanically attached to the charged fiber layer, and a second opensupport layer downstream and mechanically attached to the charged fiberlayer). In certain embodiments, the filter media may comprise an opensupport layer disposed between two charged fiber layers (e.g., a firstcharged fiber layer upstream and mechanically attached to the opensupport layer and a second charged fiber layer downstream andmechanically attached to the open support layer). For example, referringagain to FIG. 1B, in certain embodiments, filter media 102 may comprisean open support layer (i.e. first layer 110) disposed between a firstcharged layer (i.e. second layer 120) and a second charged layer (i.e.third layer 122).

Any suitable number of charged fiber layers may be present in the filtermedia. In some embodiments, the filter media may comprise one or more,two or more, three or more, or four or more charged fibers layers, oneor more of which is mechanically attached to an open support layer. Incertain embodiments, the filter media may comprise five or fewer, fouror fewer, three or fewer, or two fewer charged fiber layers, one or moreof which is mechanically attached to an open support layer. Combinationsof the above-referenced ranges are also possible (e.g., 1-5 chargedfiber layers). Other ranges are also possible.

Similarly, any suitable number of open support layers may be present inthe filter media. In some embodiments, the filter media may comprise oneor more, two or more, three or more, or four or more open supportlayers, one or more of which is mechanically attached to a charged fiberlayer. In certain embodiments, the filter media may comprise five orfewer, four or fewer, three or fewer, or two fewer open support layers,one or more of which is mechanically attached to an charged fiber layer.Combinations of the above-referenced ranges are also possible (e.g., 1-5open support layers). Other ranges are also possible.

Filter media having a charged fiber layer mechanically attached to anopen support layer as described herein may have desirable structuralproperties such as overall basis weight and/or overall thickness. Insome embodiments, the filter media may have an overall basis weight ofgreater than or equal to 12 g/m², greater than or equal to 20 g/m²,greater than or equal to 25 g/m², greater than or equal to 30 g/m²,greater than or equal to 40 g/m², greater than or equal to 50 g/m²,greater than or equal to 60 g/m², greater than or equal to 70 g/m²,greater than or equal to 80 g/m², greater than 85 g/m², greater than orequal to 90 g/m², greater than or equal to 100 g/m², greater than orequal to 150 g/m², greater than or equal to 200 g/m² g/m², greater thanor equal to 250 g/m², greater than or equal to 300 g/m², greater than orequal to 350 g/m², greater than or equal to 400 g/m², greater than orequal to 450 g/m², greater than or equal to 500 g/m², greater than orequal to 550 g/m², greater than or equal to 600 g/m², greater than orequal to 650 g/m², or greater than or equal to 700 g/m². In someembodiments, the filter media may have an overall basis weight of lessthan or equal to 750 g/m², less than or equal to 700 g/m², less than orequal to 650 g/m², less than or equal to 600 g/m², less than or equal to550 g/m², less than or equal to 500 g/m², less than or equal to 450g/m², less than or equal to 400 g/m², less than or equal to 350 g/m²,less than or equal to 300 g/m², less than or equal to 250 g/m², lessthan or equal to 200 g/m², less than or equal to 150 g/m², less than orequal to 100 g/m², less than or equal to 90 g/m², less than or equal to85 g/m², less than or equal to 80 g/m², less than or equal to 70 g/m²,less than or equal to 60 g/m², less than or equal to 50 g/m², less thanor equal to 40 g/m², less than or equal to 30 g/m², less than or equalto 25 g/m², or less than or equal to 20 g/m². Combinations of theabove-referenced ranges are also possible (e.g., an overall basis weightof greater than or equal to 12 g/m² and less than or equal to 750 g/m²,greater than or equal to 25 g/m² and less than or equal to 650 g/m²).Other values of overall basis weight are also possible. The overallbasis weight may be determined according to test standard ASTM D-846.

In some embodiments, the filter media (e.g., the filter media having acharged fiber layer mechanically attached to an open support layer) mayhave an overall thickness of greater than or equal to 5 mils, greaterthan or equal to 10 mils, greater than or equal to 15 mils, greater thanor equal to 20 mils, greater than or equal to 30 mils, greater than orequal to 40 mils, greater than or equal to 50 mils, greater than orequal to 100 mils, greater than or equal to 150 mils, greater than orequal to 200 mils, greater than or equal to 250 mils, greater than orequal to 300 mils, greater than or equal to 350 mils, greater than orequal to 400 mils, greater than or equal to 450 mils, greater than orequal to 500 mils, or greater than or equal to 550 mils. In certainembodiments, the filter media has an overall thickness of less than orequal to 600 mils, less than or equal to 550 mils, less than or equal to500 mils, less than or equal to 450 mils, less than or equal to 400mils, less than or equal to 350 mils, less than or equal to 300 mils,less than or equal to 250 mils, less than or equal to 200 mils, lessthan or equal to 150 mils, less than or equal to 100 mils, less than orequal to 50 mils, less than or equal to 40 mils, less than or equal to30 mils, less than or equal to 20 mils, less than or equal to 15 mils,or less than or equal to 10 mils. Combinations of the above-referencedranges are also possible (e.g., an overall thickness of greater than orequal to 5 mils and less than or equal to 600 mils, greater than orequal to 30 mils and less than or equal to 350 mils). Other values ofoverall thickness are also possible. The overall thickness may bedetermined according to test standard ASTM D-1777.

Filter media having a charged fiber layer mechanically attached to anopen support layer as described herein may have desirable filtrationproperties such as gamma, normalized gamma, pressure drop, and/oroverall air permeability.

The filter media (e.g., the filter media comprising an open supportlayer mechanically attached to a charged fiber layer) may exhibitsuitable overall air permeability characteristics. In some embodiments,the overall air permeability of a filter media may range from betweenabout 30 CFM and about 1100 CFM. In some embodiments, the overall airpermeability of the filter media may be greater than or equal to 30 CFM,greater than or equal to 50 CFM, greater than or equal to 75 CFM,greater than or equal to 100 CFM, greater than or equal to 150 CFM,greater than or equal to 200 CFM, greater than or equal to 300 CFM,greater than or equal to 400 CFM, greater than or equal to 500 CFM,greater than or equal to 600 CFM, greater than or equal to 700 CFM,greater than or equal to 800 CFM, greater than or equal to 900 CFM, orgreater than or equal to 1000 CFM. In certain embodiments, the filtermedia has an overall air permeability of less than or equal to 1100 CFM,less than or equal to 1000 CFM, less than or equal to 900 CFM, less thanor equal to 800 CFM, less than or equal to 700 CFM, less than or equalto 600 CFM, less than or equal to 500 CFM, less than or equal to 400CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, lessthan or equal to 100 CFM, less than or equal to 75 CFM, or less than orequal to 50 CFM. Combinations of the above-referenced ranges are alsopossible (e.g., an air permeability of greater than or equal to 30 CFMand less than or equal to 1100 CFM). Other ranges are also possible.Overall air permeability of the filter media, as determined herein, ismeasured according to the test standard ASTM D737 over 38 cm² surfacearea of the media and using a pressure of 125 Pa.

The pressure drop across the filter media (e.g., the filter mediacomprising an open support layer mechanically attached to a chargedfiber layer) may vary depending on the particular application of thefilter media. In some embodiments, for example, the pressure drop acrossthe filter media may range from between 1 Pa and 120 Pa, or between 1 Paand 100 Pa. In some embodiments, the pressure drop across the filtermedia may be greater than or equal to 1 Pa, greater than or equal to 2Pa, greater than or equal to 5 Pa, greater than or equal to 10 Pa,greater than or equal to 20 Pa, greater than or equal to 30 Pa, greaterthan or equal to 40 Pa, greater than or equal to 50 Pa, greater than orequal to 60 Pa, greater than or equal to 70 Pa, greater than or equal to80 Pa, greater than or equal to 90 Pa, greater than or equal to 100 Pa,or greater than or equal to 110 Pa. In certain embodiments, the pressuredrop across the filter media may be less than or equal to 120 Pa, lessthan or equal to 110 Pa, less than or equal to 100 Pa, less than orequal to 90 Pa, less than or equal to 80 Pa, less than or equal to 70Pa, less than or equal to 60 Pa, less than or equal to 50 Pa, less thanor equal to 40 Pa, less than or equal to 30 Pa, less than or equal to 20Pa, less than or equal to 10 Pa, less than or equal to 5 Pa, or lessthan or equal to 2 Pa. Combinations of the above-referenced ranges arealso possible (e.g., a pressure drop of greater than or equal 1 Pa andless than or equal to 120 Pa, greater than or equal to 1 Pa and lessthan or equal to 100 Pa). Other ranges are also possible.

The pressure drop is measured as the differential pressure across thefilter media or fiber layer when exposed to NaCl aerosol at a facevelocity of 95 liters per minute. The face velocity is the velocity ofair as it hits the upstream side of the filter media or filtrationlayer. Values of pressure drop are typically recorded as millimeters ofwater or Pascals. The values of pressure drop described herein weredetermined according to EN13274-7 standard. The pressure drop value ismeasured with NaCl aerosol of particle size 0.65 micron with a facevelocity of 95 liters/min over an area of 100 cm².

In some embodiments, the filter media may have a desirable normalizedefficiency. For instance, in some embodiments, the normalized efficiencyof the filter media may be greater than or equal to 1, greater than orequal to 1.25, greater than or equal to 1.5, greater than or equal to 2,greater than or equal to 2.5, or greater than or equal to 3. In certainembodiments, the filter media may have a normalized efficiency of lessthan or equal to 3.5, less than or equal to 3, less than or equal to2.5, less than or equal to 2, or less than or equal to 1.5. Combinationsof the above-referenced ranges are also possible (e.g., greater than orequal to 1 and less than or equal to 3.5). Other values of thenormalized efficiency of the filter media are also possible. Normalizedefficiency is provided without units and refers to the ratio of theinitial efficiency percentage of the filter media to the total basisweight (measured in g/m²) of the one or more charged fiber layers withinthe filter media (i.e. not including any open support layers or coarsesupport layers). Initial efficiency was determined according toEN13274-7 standard using NaCl aerosol of particle size 0.65 micron witha face velocity of 95 liters/min over an area of 100 cm².

Advantageously, filter media comprising an open support layer (e.g.,having an air permeability greater than 1100 CFM) mechanically attached(e.g., needled) to a charged fiber layer may exhibit a decreasedpressure drop and/or increased dust holding capacity as compared to afilter media with a support layer having an air permeability less thanor equal to 1100 CFM adjacent to the charged fiber layer.

In some embodiments, the filter media may have a certain dust holdingcapacity. For instance, in some embodiments, the filter media may have adust holding capacity of greater than or equal to 1 g/m², greater thanor equal to 5 g/m², greater than or equal to 10 g/m², greater than orequal to 20 g/m², greater than or equal to 30 g/m², greater than orequal to 40 g/m², greater than or equal to 50 g/m², greater than orequal to 60 g/m², greater than or equal to 70 g/m², greater than orequal to 80 g/m², greater than or equal to 90 g/m², greater than orequal to 100 g/m², greater than or equal to 110 g/m², greater than orequal to 120 g/m², or greater than or equal to 130 g/m². In certainembodiments, the dust holding capacity of the filter media may be lessthan or equal to 140 g/m², less than or equal to 130 g/m², less than orequal to 120 g/m², less than or equal to 110 g/m², less than or equal to100 g/m², less than or equal to 90 g/m², less than or equal to 80 g/m²,less than or equal to 70 g/m², less than or equal to 60 g/m², less thanor equal to 50 g/m², less than or equal to 40 g/m², less than or equalto 30 g/m², less than or equal to 20 g/m², less than or equal to 10g/m², or less than or equal to 5 g/m². Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto about 1 g/m² and less than or equal to about 140 g/m², greater thanor equal to about 80 g/m² and less than or equal to about 140 g/m²).Other values of dust holding capacity are also possible. The dustholding capacity of a filter media comprising an open support layermechanically attached to a charged fiber layer, not in a wavedconfiguration is tested based upon standard ISO/TS 11155-1. The testinguses ISO 12103-1, A2 fine test dust at a base upstream gravimetric dustlevel of 75 mg/m³. The test is run at a face velocity of 20 cm/sec overa filter area of 100 cm² until filter media reaches an air resistance of82 Pa.

Because it may be desirable to rate filter media or layer based on therelationship between penetration and pressure drop across the media, orparticulate efficiency as a function of pressure drop across the mediaor web, filters may be rated according to a value termed gamma value.Generally, higher gamma values are indicative of better filterperformance, i.e., a high particulate efficiency as a function ofpressure drop. Gamma value is expressed according to the followingformula:

gamma=(−log(initial NaCl penetration %/100)/pressure drop, Pa)×100×9.8,which is equivalent to: gamma=(−log(initial NaCl penetration%/100)/pressure drop, mm H₂O)×100.

The NaCl penetration percentage is based on the percentage of particlesthat penetrate through the filter media or layer. With decreased NaClpenetration percentage (i.e., increased particulate efficiency) whereparticles are less able to penetrate through the filter media or layer,gamma increases. With decreased pressure drop (i.e., low resistance tofluid flow across the filter), gamma increases. These generalizedrelationships between NaCl penetration, pressure drop, and/or gammaassume that the other properties remain constant.

Penetration, often expressed as a percentage, is defined as follows: Pen(%)=(C/C₀)*100 where C is the particle concentration after passagethrough the filter and C₀ is the particle concentration before passagethrough the filter. Typical tests of penetration involve blowing sodiumchloride (NaCl) particles through a filter media or layer and measuringthe percentage of particles that penetrate through the filter media orlayer. Penetration and pressure drop values described herein weredetermined using an 8130 CertiTest™ automated filter testing unit fromTSI, Inc. equipped with a sodium chloride generator for NaCl aerosoltesting based on EN13274-7 standard for NaCl particles. The averageparticle size created by the salt particle generator was 0.65 micronmass mean diameter. The instrument measured a pressure drop across thefilter media and the resultant penetration value on an instantaneousbasis. The initial penetration is the first taken at the beginning ofthe test and can be used to determine the initial efficiency of thefilter media. Pressure drop values (e.g., for determining gamma) aredetermined using the EN13274-7 standard on a sodium flame photometerfrom SFP Services Ltd, UK. The instrument measures a pressure dropacross the filter media (or layer) when the filter media or layer issubjected to a 95 liters/min face velocity over an area of 100 cm².

The filter media (e.g., the filter media comprising an open supportlayer mechanically attached to a charged fiber layer) as a whole mayhave a relatively high value of gamma. In some embodiments, the value ofgamma for the filter is greater than or equal to 30, greater than orequal to 50, greater than or equal to 75, greater than or equal to 100,greater than or equal to 125, greater than or equal to 150, greater thanor equal to 175, greater than or equal to 200, or greater than or equalto 225. In some embodiments, the value of gamma for the filter media isless than or equal to 250, less than or equal to 225, less than or equalto 200, less than or equal to 175, less than or equal to 150, less thanor equal to 125, less than or equal to 100, less than or equal to 75, orless than or equal to 50. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to 30 and less than orequal to 250, or greater than or equal to 75 and less than or equal to150). Other ranges are also possible.

The filter media (e.g., the filter media comprising an open supportlayer mechanically attached to a charged fiber layer) may have adesirable normalized gamma. Normalized gamma, as used herein, is aunitless parameter and refers to the ratio of the gamma of the filtermedia to the total basis weight (measured in g/m²) of the one or morecharged fiber layers within the filter media (i.e. not including anyopen support layers or coarse support layers). In some embodiments, thenormalized gamma of the filter media (e.g., the filter media comprisingan open support layer mechanically attached to a charged fiber layer)may be greater than or equal to 1, greater than or equal to 1.5, greaterthan or equal to 2, greater than or equal to 2.5, greater than or equalto 3, greater than or equal to 3.5, greater than or equal to 4, greaterthan or equal to 4.5, greater than or equal to 5, greater than or equalto 5.5, greater than or equal to 5.6, greater than or equal to 6,greater than or equal to, greater than or equal to 6.5, greater than orequal to 7, greater than or equal to 7.5, greater than or equal to 8,greater than or equal to 8.5, greater than or equal to 9, greater thanor equal to 9.5, greater than or equal to 10, or greater than or equalto 10.5. In certain embodiments, the normalized gamma of the filtermedia may be less than or equal to 10.9, less than or equal to 10.5,less than or equal to 10, less than or equal to 9.5, less than or equalto 9, less than or equal to 8.5, less than or equal to 8, less than orequal to 7.5, less than or equal to 7, less than or equal to 6.5, lessthan or equal to 6, less than or equal to 5.6, less than or equal to5.5, less than or equal to 5, less than or equal to 4.5, less than orequal to 4, less than or equal to 3.5, less than or equal to 3, lessthan or equal to 2.5, less than or equal to 2, or less than or equal to1.5. Combinations of the above-referenced ranges are also possible(e.g., a normalized gamma of the filter media of greater than or equalto 1 and less than or equal to 10.9, greater than or equal to 1 and lessthan or equal to 5.6). Other ranges are also possible. For example, inan exemplary embodiment, the filter media comprises a charged fiberlayer comprising a plurality of fibers and the filter media has anormalized gamma of greater than or equal to 1 and less than or equal to5.6. In another exemplary embodiment, the filter media comprises aplurality of fibers a charged fiber layer comprising a plurality offibers that are relatively fine (e.g., having an average fiber diameterless than 15 microns) and the filter media has a normalized gamma ofgreater than or equal to 1 and less than or equal to 10.9.

As described herein, a filter media and/or a layer (e.g., a first layer,a second layer) may be designed to have a penetration or efficiency(e.g., initial efficiency). Penetration and (initial) efficiency aremeasured as described above. In general, (initial) efficiency isdetermined as 100−% Penetration. Penetration, expressed as a percentage,is defined as Pen=(C/C₀)*100, where C is the particle concentrationafter passage through the filter media and C₀ is the particleconcentration before passage through the filter media.

In some embodiments, the initial efficiency of the filter media isgreater than or equal to 50% greater than or equal to 55% greater thanor equal to 60% greater than or equal to 65% greater than or equal to70% greater than or equal to 75% greater than or equal to 80% greaterthan or equal to 85% greater than or equal to 90%, greater than or equalto 92%, greater than or equal to 95%, greater than or equal to 96%,greater than or equal to 97%, greater than or equal to 98%, greater thanor equal to 99%, greater than or equal to 99.5%, greater than or equalto 99.8%, greater than or equal to 99.9%, or greater than or equal to99.99%. In some embodiments, the initial efficiency of the filter mediais less than or equal to 99.999%, less than or equal to 99.99%, lessthan or equal to 99.9%, less than or equal to 99.8%, less than or equalto 99.5%, less than or equal to 99%, less than or equal to 98%, lessthan or equal to 97%, less than or equal to 96%, less than or equal to95%, less than or equal to 92%, less than or equal to 90%, less than orequal to 85%, less than or equal to 80%, less than or equal to 75%, lessthan or equal to 70%, less than or equal to 65%, less than or equal to60%, or less than or equal to 55%. Combinations of the above-referencedranges are also possible (e.g., an initial efficiency of greater than orequal to 50% and less than or equal to 99.999%, greater than or equal to90% and less than or equal to 99.999%). Other ranges are also possible.Initial efficiency is determined as described above.

In an exemplary embodiment, the filter media may comprise an opensupport layer and a charged fiber layer mechanically attached to theopen support layer, wherein the open support layer has an airpermeability of greater than 1100 CFM and less than or equal to 20000CFM and is a mesh. In some embodiments, the open support layer has asolidity of less than or equal to 10%.

In another exemplary embodiment, the filter media may comprise an opensupport layer and a charged fiber layer mechanically attached to theopen support layer, wherein the open support layer has an airpermeability of greater than 1100 CFM and less than or equal to 20000CFM. In some embodiments, the filter media has an overall basis weightof greater than or equal to 12 g/m² and less than or equal to 700 g/m²,a gamma greater than or equal to 90 and less than or equal to 250,and/or an overall air permeability of greater than or equal to 30 CFMand less than or equal to 1100 CFM. In some cases, the charged fiberlayer may be needled to the open support layer.

In some embodiments, the filter media may comprise at least one layer(e.g., a charged fiber layer) that is held in a waved or curvilinearconfiguration. In certain embodiments, the filter media (and/or one ormore open support layers of the filter media) are held in a waved orcurvilinear configuration by one or more additional support layers(e.g., one or more coarse support layers). As a result of the wavedconfiguration, advantageously, the filter media may have an increasedsurface area which can result in improved filtration properties. Thefilter media may include various layers (e.g., an open support layer,one or more fiber layers such as charged fiber layers, a coarse supportlayer, a top and/or bottom layer), and only some or all of the layersmay be waved. Advantageously, the filter media having at least one layerthat is held in a waved or curvilinear configuration as describedherein, may comprise a relatively charged fiber layer having arelatively low basis weight.

In some embodiments, an open support layer such as a mesh may provideadditional mechanical reinforcement and/or structural stability (e.g.,to a filter media having a waved configuration) while having arelatively high air permeability. FIG. 2A illustrates one exemplaryembodiment of the filter media 200 having a first layer 210 (e.g., anopen support layer such as a mesh) and a second layer 220 (e.g., acharged fiber layer) adjacent first layer 210. In the illustratedembodiment, first layer 210 and second layer 220 are in a wavedconfiguration comprising peaks and troughs of adjacent waves of thefilter media. As illustrated in FIG. 2B, in some embodiments, filtermedia 202 comprises first layer 210 (e.g. open support layer such as amesh) disposed between second layer 220 (e.g., a first charged fiberlayer) and third layer 222 (e.g., a second charged fiber layer).

In certain embodiments, the filter media comprises a coarse supportlayer that holds the filtration layer in a waved configuration tomaintain separation of peaks and troughs of adjacent waves of thefiltration layer. As illustrated in FIG. 2C, filter media 204 includes afirst layer 210 (e.g., an open support layer such as a mesh) disposedbetween second layer 220 (e.g., a first charged fiber layer) and thirdlayer 230 (e.g., a second charged fiber layer). In the illustratedembodiment, filter media 204 comprises a first coarse support layer 230adjacent second layer 220 and a second coarse support layer 232 adjacentthird layer 222. Coarse support layers 230 and 232 can help maintain thesecond layer 220 and third layer 230, and optionally any additionallayers (e.g., the open support layer), in the waved configuration. Whiletwo coarse support layers 230, 232 are shown, the filter media 204 neednot include both coarse support layers. Where only one support layer isprovided, the support layer can be disposed upstream or downstream ofthe filtration layer(s).

The filter media 204 can also optionally include one or more outer orcover layers located on the upstream-most and/or downstream-most sidesof the filter media 204. FIG. 2C illustrates a top layer 240 disposed onthe upstream side of the filter media 204 to function, for example, asan upstream dust holding layer and/or a support layer. The top layer 240can also function as an aesthetic layer, which will be discussed in moredetail below. The layers in the illustrated embodiment are arranged sothat the top layer 240 is disposed on the air entering side, labeled I,the first coarse support layer 230 is just downstream of the top layer240, the second fiber layer 220 is disposed just downstream of the firstcoarse support layer 230, the open support layer 210 is disposeddownstream of the second fiber layer 220, the third fiber layer 222 isdisposed downstream of the open support layer 210, and the second coarsesupport layer 232 is disposed downstream of the third fiber layer 222 onthe air outflow side, labeled O. The direction of air flow, i.e., fromair entering I to air outflow O, is indicated by the arrows marked withreference A. The outer or cover layer can alternatively or additionallybe a bottom layer disposed on the downstream side of the filter media204 to function as a strengthening component that provides structuralintegrity to the filter media 204 to help maintain the wavedconfiguration. The outer or cover layer(s) can also function to offerabrasion resistance.

Furthermore, as shown in the exemplary embodiment illustrated in FIG.2C, the outer or cover layer(s) can have a topography different from thetopographies of the fiber filtration layer and/or any support layers.For example, in either a pleated or non-pleated configuration, the outeror cover layer(s) may be non-waved (e.g., substantially planar), whereasthe fiber layer(s) and/or any open support layers may have a wavedconfiguration. A person skilled in the art will appreciate that avariety of other configurations are possible, and that the filter mediacan include any number of layers in various arrangements.

As shown illustratively in FIGS. 2C-2D, the fiber layers and/or supportlayers may have waved configuration including a plurality of peaks P andtroughs T with respect to each surface thereof. A person skilled in theart may appreciate that a peak P on one side of the filtration layer mayhave a corresponding trough T on the opposite side. Thus, second layer220 may extend into a trough T, and exactly opposite that same trough Tis a peak P, across which upstream third layer 222 may extend. Peaks andtroughs may also be present in a single filtration layer as shownillustratively in FIG. 2D. As shown illustratively in FIG. 2C, thetroughs may be partially or substantially filled with fibers (e.g.,partially or substantially filled with the coarse support layer).

Some or all of the fiber layers, and/or some or all of the supportlayers (e.g., the open support layer, one or more coarse support layers)can be formed into a waved configuration using various manufacturingtechniques, but in an exemplary embodiment involving a single fiberlayer, the fiber layer is positioned on a first moving surface adjacentto a second moving surface, and the fiber layer is conveyed between thefirst and second moving surfaces that are traveling at different speeds.In an example involving two or more fiber layers, the fiber layers arepositioned adjacent to one another in a desired arrangement from airentering side to air outflow side, and the combined layers are conveyedbetween first and second moving surfaces that are traveling at differentspeeds. For instance, the second surface may be traveling at a speedthat is slower than the speed of the first surface. In eitherarrangement, a suction force, such as a vacuum force, can be used topull the layer(s) toward the first moving surface, and then toward thesecond moving surface as the layer(s) travel from the first to thesecond moving surfaces. The speed difference causes the layer(s) to formZ-direction waves as they pass onto the second moving surface, thusforming peaks and troughs in the layer(s). The speed of each surface aswell as the ratio of speeds between the two surfaces can be altered toobtain a percentage of fiber orientations as described herein.Generally, a higher ratio of speeds results in a higher percentage offibers having a more angled orientation with respect to the horizontal,or with respect to a surface (e.g., a planar surface) of the fiber layeror an outer or cover layer. In some embodiments, one or more fiberlayers, or a filter media, is formed using a ratio of speeds of at least1.5, at least 2.5, at least 3.5, at least 4.0, at least 4.5, at least5.0, at least 5.5, or at least 6.0. In certain embodiments, the ratio ofspeeds is less than or equal to 10.0, less than or equal to 9.0, lessthan or equal to 8.0, less than or equal to 7.0, less than or equal to6.0, less than or equal to 5.0, or less than or equal to 4.0, less thanor equal to 3.5, less than or equal to 3.0, or less than or equal to2.5. Combinations of the above-referenced ranges are also possible.Other ratios are also possible.

The speed of each surface can be also altered to obtain the desirednumber of waves per inch. The distance between the surfaces can also bealtered to determine the amplitude of the peaks and troughs, and in anexemplary embodiment the distance is adjusted between 0 to 2″. Theproperties of the different layers can also be altered to obtain adesired filter media configuration.

In some embodiments, the periodicity (e.g., the number of waves perinch) of the second layer (e.g., the charged fiber layer) may rangebetween 10 and 40 waves per 6 inches (e.g., between 3 and 15 waves per 6inches, between 5 and 9 waves per 6 inches). In some embodiments, theperiodicity of the filtration layer may be greater than or equal to 3waves, greater than or equal to 4 waves, greater than or equal to 5waves, greater than or equal to 6 waves, greater than or equal to 7waves, greater than or equal to 8 waves, greater than or equal to 9waves, greater than or equal to 10 waves, greater than or equal to 11waves, greater than or equal to 12 waves, greater than or equal to 13waves, greater than or equal to 14 waves, greater than or equal to 15waves, greater than or equal to 17 waves, greater than or equal to 20waves, greater than or equal to 25 waves, greater than or equal to 30waves, or greater than or equal to 35 waves per 6 inches. In certainembodiments, the periodicity of the second layer may be less than orequal to 40 waves, less than or equal to 35 waves, less than or equal to30 waves, less than or equal to 25 waves, less than or equal to 20waves, less than or equal to 17 waves, less than or equal to 15 waves,less than or equal to 14 waves, less than or equal to 13 waves, lessthan or equal to 12 waves, less than or equal to 11 waves, less than orequal to 10 waves, less than or equal to 9 waves, less than or equal to8 waves, less than or equal to 7 waves, less than or equal to 6 waves,less than or equal to 5 waves, or less than or equal to 4 waves per 6inches. Combinations of the above-referenced ranges are also possible(e.g., a periodicity of the second layer of greater than or equal to 10and less than or equal to 40 waves per 6 inches, greater than or equalto 5 and less than or equal to 9 waves per 6 inches, greater than orequal to 3 and less than or equal to 15 waves per 6 inches). Otherranges of periodicities are also possible. Additionally, in embodimentsin which one or more layers (e.g., a third layer such as a secondcharged fiber layer) are present in a media, each layer may have aperiodicity having one or more of the above-referenced ranges.

Any suitable number of charged fiber layers may be present in the filtermedia (e.g., the filter media comprising an open support layer and oneor more charged fiber layers, where at least one charged fiber layer isheld in a waved or curvilinear configuration). In some embodiments, thefilter media may comprise one or more, two or more, three or more, orfour or more charged fibers layers, one or more of which is mechanicallyattached to an open support layer. In certain embodiments, the filtermedia may comprise five or fewer, four or fewer, three or fewer, or twofewer charged fiber layers, one or more of which is mechanicallyattached to an open support layer. Combinations of the above-referencedranges are also possible (e.g., 1-5 charged fiber layers). Other rangesare also possible.

Similarly, any suitable number of open support layers may be present inthe filter media. In some embodiments, the filter media may comprise oneor more, two or more, three or more, or four or more open supportlayers, one or more of which is mechanically attached to a charged fiberlayer. In certain embodiments, the filter media may comprise five orfewer, four or fewer, three or fewer, or two fewer open support layers,one or more of which is mechanically attached to an charged fiber layer.Combinations of the above-referenced ranges are also possible (e.g., 1-5charged fiber layers). Other ranges are also possible.

Filter media having an open support layer, a coarse support layer, and acharged fiber layer, where at least the charged fiber layer is held in awaved or curvilinear configuration as described herein may havedesirable structural properties such as overall basis weight. In someembodiments, the filter media may have an overall basis weight ofgreater than or equal to 30 g/m², greater than or equal to 40 g/m²,greater than or equal to 50 g/m², greater than or equal to 60 g/m²,greater than or equal to 70 g/m², greater than or equal to 80 g/m²,greater than 85 g/m², greater than or equal to 90 g/m², greater than orequal to 100 g/m², greater than or equal to 150 g/m², greater than orequal to 200 g/m² g/m², greater than or equal to 250 g/m², greater thanor equal to 300 g/m², greater than or equal to 350 g/m², greater than orequal to 400 g/m², greater than or equal to 450 g/m², greater than orequal to 500 g/m², greater than or equal to 550 g/m², greater than orequal to 600 g/m², greater than or equal to 650 g/m², greater than orequal to 700 g/m², or greater than or equal to 750 g/m². In someembodiments, the filter media may have an overall basis weight of lessthan or equal to 800 g/m², less than or equal to 750 g/m², less than orequal to 700 g/m², less than or equal to 650 g/m², less than or equal to600 g/m², less than or equal to 550 g/m², less than or equal to 500g/m², less than or equal to 450 g/m², less than or equal to 400 g/m²,less than or equal to 350 g/m², less than or equal to 300 g/m², lessthan or equal to 250 g/m², less than or equal to 200 g/m², less than orequal to 150 g/m², less than or equal to 100 g/m², less than or equal to90 g/m², less than or equal to 85 g/m², less than or equal to 80 g/m²,less than or equal to 70 g/m², less than or equal to 60 g/m², less thanor equal to 50 g/m², or less than or equal to 40 g/m². Combinations ofthe above-referenced ranges are also possible (e.g., an overall basisweight of greater than or equal to 30 g/m² and less than or equal to 800g/m², greater than or equal to 100 g/m² and less than or equal to 450g/m²). Other values of overall basis weight are also possible. Theoverall basis weight may be determined according to test standard ASTMD-846.

In some embodiments, the filter media (e.g., the filter media comprisingan open support layer, a coarse support layer, and one or more chargedfiber layers, where at least one charged fiber layer is held in a wavedor curvilinear configuration) has a particular thickness. In certainembodiments, the thickness of the overall filter media is greater thanor equal to 100 mil, greater than or equal to 150 mil, greater than orequal to 200 mil, greater than or equal to 250 mil, greater than orequal to 300 mil, greater than or equal to 400 mil, greater than orequal to 500 mil, greater than or equal to 600 mil, greater than orequal to 700 mil, greater than or equal to 800 mil, greater than orequal to 900 mil, greater than or equal to 1000 mil, greater than orequal to 1500 mil, greater than or equal to 2000 mil, greater than orequal to 2500 mil, greater than or equal to 3000 mil, or greater than orequal to 3500 mil. In some embodiments, the thickness of the overallfilter media is less than or equal to 4000 mil, less than or equal to3500 mil, less than or equal to 3000 mil, less than or equal to 2500mil, less than or equal to 2000 mil, less than or equal to 1500 mil,less than or equal to 1000 mil, less than or equal to 900 mil, less thanor equal to 800 mil, less than or equal to 700 mil, less than or equalto 600 mil, less than or equal to 500 mil, less than or equal to 400mil, less than or equal to 300 mil, less than or equal to 250 mil, lessthan or equal to 200 mil, or less than or equal to 150 mil. Combinationsof the above-referenced ranges are also possible (e.g., a thickness ofgreater than or equal to 100 mil and less than or equal to 4000 mil,greater than 150 mil and less than or equal to 1000 mil). Other rangesare also possible. Thickness of the overall filter media as determinedherein is measured according to TAPPI T411.

Filter media having an open support layer, a coarse support layer, andone or more charged fiber layers, where at least one charged fiber layeris held in a waved or curvilinear configuration as described herein mayhave desirable filtration properties such as dust holding capacity,gamma, pressure drop, and/or overall air permeability.

The filter media (e.g., the filter media comprising an open supportlayer, a coarse support layer, and one or more charged fiber layers,where at least one charged fiber layer is held in a waved or curvilinearconfiguration) may exhibit suitable overall air permeabilitycharacteristics. In some embodiments, the overall air permeability of afilter media may range from between about 10 CFM and about 1000 CFM. Insome embodiments, the overall air permeability of the filter media maybe greater than or equal to 10 CFM, greater than or equal to 25 CFM,greater than or equal to 50 CFM, greater than or equal to 75 CFM,greater than or equal to 100 CFM, greater than or equal to 150 CFM,greater than or equal to 200 CFM, greater than or equal to 300 CFM,greater than or equal to 400 CFM, greater than or equal to 500 CFM,greater than or equal to 600 CFM, greater than or equal to 700 CFM,greater than or equal to 800 CFM, or greater than or equal to 900 CFM.In certain embodiments, the filter media has an overall air permeabilityof less than or equal to 1000 CFM, less than or equal to 900 CFM, lessthan or equal to 800 CFM, less than or equal to 700 CFM, less than orequal to 600 CFM, less than or equal to 500 CFM, less than or equal to400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM,less than or equal to 100 CFM, less than or equal to 75 CFM, less thanor equal to 50 CFM, or less than or equal to 25 CFM. Combinations of theabove-referenced ranges are also possible (e.g., an air permeability ofgreater than or equal to 10 CFM and less than or equal to 1000 CFM,greater than or equal to 100 CFM and less than or equal to 700 CFM).Other ranges are also possible. Overall air permeability of the filtermedia, as determined herein, is measured according to the test standardASTM D737 over 38 cm² surface area of the media and using a pressure of125 Pa.

The pressure drop across the filter media (e.g., the filter mediacomprising an open support layer, a coarse support layer, and one ormore charged fiber layers, where at least one charged fiber layer isheld in a waved or curvilinear configuration) may vary depending on theparticular application of the filter media. In some embodiments, forexample, the pressure drop across the filter media may range frombetween 2 Pa and 200 Pa, or between 3 Pa and 25 Pa. In some embodiments,the pressure drop across the filter media may be greater than or equalto 2 Pa, greater than or equal to 3 Pa, greater than or equal to 5 Pa,greater than or equal to 10 Pa, greater than or equal to 20 Pa, greaterthan or equal to 25 Pa, greater than or equal to 50 Pa, greater than orequal to 75 Pa, greater than or equal to 100 Pa, greater than or equalto 125 Pa, greater than or equal to 150 Pa, or greater than or equal to175 Pa. In certain embodiments, the pressure drop across the filtermedia may be less than or equal to 200 Pa, less than or equal to 175 Pa,less than or equal to 150 Pa, less than or equal to 125 Pa, less than orequal to 100 Pa, less than or equal to 75 Pa, less than or equal to 50Pa, less than or equal to 25 Pa, less than or equal to 20 Pa, less thanor equal to 10 Pa, less than or equal to 5 Pa, or less than or equal to3 Pa. Combinations of the above-referenced ranges are also possible(e.g., a pressure drop of greater than or equal 2 Pa and less than orequal to 200 Pa, greater than or equal to 3 Pa and less than or equal to25 Pa). Other ranges are also possible.

The filter media described herein can have beneficial dust holdingproperties. In some embodiments, the filter media (e.g., the filtermedia comprising an open support layer, a coarse support layer, and oneor more charged fiber layers, where at least one charged fiber layer isheld in a waved or curvilinear configuration) may have a dust holdingcapacity (DHC) of greater than or equal to 5 g/m², greater than or equalto 10 g/m², greater than or equal to 25 g/m², greater than or equal to50 g/m², greater than or equal to 75 g/m², greater than or equal to 100g/m², greater than or equal to 150 g/m², greater than or equal to 200g/m², greater than or equal to 250 g/m², greater than or equal to 300g/m², greater than or equal to 350 g/m², greater than or equal to 400g/m², greater than or equal to 450 g/m², greater than or equal to 500g/m², or greater than or equal to 550 g/m². In some embodiments, the DHCof the filter media may be less than or equal to 600 g/m², less than orequal to 550 g/m², less than or equal to 500 g/m², less than or equal to450 g/m², less than or equal to 400 g/m², less than or equal to 350g/m², less than or equal to 300 g/m², less than or equal to 250 g/m²,less than or equal to 200 g/m², less than or equal to 150 g/m², lessthan or equal to 100 g/m², less than or equal to 75 g/m², less than orequal to 50 g/m², less than or equal to 25 g/m², or less than or equalto 10 g/m². Combinations of the above-referenced ranges are alsopossible (e.g., a DHC of greater than or equal to 5 g/m² and less thanor equal to 600 g/m², greater than or equal to 200 g/m² and less than orequal to 350 g/m²). Other ranges are also possible.

The dust holding capacity of a filter media comprising an open supportlayer, a coarse support layer, and one or more charged fiber layers,where at least one charged fiber layer is held in a waved or curvilinearconfiguration is tested based on the ASHRAE 52.2 standard. The testinguses ASHRAE test dust at a base upstream gravimetric dust level of 70mg/m². The test is run at a face velocity of 0.944 m³/s (3400 m³/h)until a terminal pressure of 450 Pa.

The filter media (e.g., the filter media comprising an open supportlayer and one or more charged fiber layers, where at least one chargedfiber layer is held in a waved or curvilinear configuration) as a wholemay have a relatively high value of gamma. In some embodiments, thevalue of gamma for the filter is greater than or equal to 20, greaterthan or equal to 30, greater than or equal to 50, greater than or equalto 75, greater than or equal to 100, greater than or equal to 125,greater than or equal to 150, greater than or equal to 175, greater thanor equal to 200, or greater than or equal to 225. In some embodiments,the value of gamma for the filter media is less than or equal to 250,less than or equal to 225, less than or equal to 200, less than or equalto 175, less than or equal to 150, less than or equal to 125, less thanor equal to 100, less than or equal to 75, less than or equal to 50, orless than or equal to 30. Combinations of the above-referenced rangesare also possible (e.g., greater than or equal to 20 and less than orequal to 250, or greater than or equal to 75 and less than or equal to150). Other ranges are also possible. Gamma is determined as describedabove.

The filter media (e.g., the filter media comprising an open supportlayer, a coarse support layer, and one or more charged fiber layers,where at least one charged fiber layer is held in a waved or curvilinearconfiguration) may be designed to have a particular initial efficiency(e.g., initial efficiency).

In some embodiments, the initial efficiency of the filter media (e.g.,the filter media comprising an open support layer, a coarse supportlayer, and one or more charged fiber layers, where at least one chargedfiber layer is held in a waved or curvilinear configuration is greaterthan or equal to 50% greater than or equal to 55% greater than or equalto 60% greater than or equal to 65% greater than or equal to 70% greaterthan or equal to 75% greater than or equal to 80% greater than or equalto 85% greater than or equal to 90%, greater than or equal to 92%,greater than or equal to 95%, greater than or equal to 96%, greater thanor equal to 97%, greater than or equal to 98%, greater than or equal to99%, greater than or equal to 99.5%, greater than or equal to 99.8%,greater than or equal to 99.9%, or greater than or equal to 99.99%. Insome embodiments, the initial efficiency of the filter media is lessthan or equal to 99.999%, less than or equal to 99.99%, less than orequal to 99.9%, less than or equal to 99.8%, less than or equal to99.5%, less than or equal to 99%, less than or equal to 98%, less thanor equal to 97%, less than or equal to 96%, less than or equal to 95%,less than or equal to 92%, less than or equal to 90%, less than or equalto 85%, less than or equal to 80%, less than or equal to 75%, less thanor equal to 70%, less than or equal to 65%, less than or equal to 60%,or less than or equal to 55%. Combinations of the above-referencedranges are also possible (e.g., an initial efficiency of greater than orequal to 50% and less than or equal to 99.999%, greater than or equal to90% and less than or equal to 99.999%). Other ranges are also possible.

In an exemplary embodiment, the filter media comprises a charged fiberlayer, an open support layer mechanically attached to the charged fiberlayer and a coarse support layer that holds the charged fiber layer in awaved configuration and maintains separation of peaks and troughs ofadjacent waves of the charged fiber layer. In some embodiments, thecharged fiber layer has a basis weight of less than or equal to 12 g/m²and greater than or equal to 700 g/m². In certain embodiments, the opensupport layer has an air permeability of greater than 1100 CFM and lessthan or equal to 20000 CFM. In some embodiments, the filter media has anoverall air permeability of greater than or equal to 10 CFM and lessthan or equal to 1000 CFM.

As described above and herein, in some embodiments, the filter mediacomprises one or more coarse support layers (e.g., that holds thecharged fiber layer in a waved configuration and maintains separation ofpeaks and troughs of adjacent waves of the charged fiber layer).

Referring again to FIG. 2C, the coarse support layers 230, 232 can beformed from a variety of fibers types and sizes. In an exemplaryembodiment, the downstream coarse support layer 232 is formed fromfibers having an average fiber diameter that is greater than or equal toan average fiber diameter of the second layer 220 and/or third layer222, the upstream coarse support layer 230, and the top layer 240, ifprovided. In some cases, the upstream support layer 230 is formed fromfibers having an average fiber diameter that is less than or equal to anaverage fiber diameter of the downstream support layer 232, but that isgreater than an average fiber diameter of the second layer 220 and/orthird layer 222.

The fibers of the coarse support layer(s) (e.g., the downstream supportlayer, the upstream support layer) may have an average fiber length of,for example, between about 0.5 inches and 6.0 inches (e.g., between 1.5inches and 3 inches). In some embodiments, the fibers of the coarsesupport layer may have an average fiber length of less than or equal to6 inches, less than or equal to 5.5 inches, less than or equal to 5inches, less than or equal to 4.5 inches, less than or equal to 4inches, less than or equal to 3.5 inches, less than or equal to 3inches, less than or equal to 2.5 inches, less than or equal to 2inches, or less than or equal to 1 inch. In certain embodiments, thefibers of the coarse support layer may have an average fiber length ofgreater than or equal to 0.5 inches, greater than or equal to 1 inch,greater than or equal to 1.5 inches, greater than or equal to 2 inches,greater than or equal to 2.5 inches, greater than or equal to 3 inches,greater than or equal to 3.5 inches, greater than or equal to 4 inches,greater than or equal to 4.5 inches, greater than or equal to 5 inches,or greater than or equal to 5.5 inches. Combinations of theabove-referenced ranges are also possible (e.g., greater than or equalto 0.5 inches and less than or equal to 6 inches, greater than or equalto 1.5 inches and less than or equal to 3 inches). Other ranges are alsopossible.

In some embodiments, the plurality of fibers in the coarse supportlayer(s) may have an average fiber diameter of greater than or equal to8 microns, greater than or equal to 10 microns, greater than or equal to12 microns, greater than or equal to 15 microns, greater than or equalto 20 microns, greater than or equal to 25 microns, greater than orequal to 30 microns, greater than or equal to 35 microns, greater thanor equal to 40 microns, greater than or equal to 45 microns, greaterthan or equal to 50 microns, greater than or equal to 55 microns,greater than or equal to 60 microns, greater than or equal to 65microns, greater than or equal to 70 microns, greater than or equal to75 microns, or greater than or equal to 80 microns. In some embodiments,the plurality of fibers in the coarse support layer(s) may have anaverage fiber diameter of less than or equal to 85 microns, less than orequal to 80 microns, less than or equal to 75 microns, less than orequal to 70 microns, less than or equal to 65 microns, less than orequal to 60 microns, less than or equal to 55 microns, less than orequal to 50 microns, less than or equal to 45 microns, less than orequal to 40 microns, less than or equal to 35 microns, less than orequal to 30 microns, less than or equal to 25 microns, less than orequal to 20 microns, less than or equal to 15 microns, less than orequal to 12 microns, or less than or equal to 10 microns. Combinationsof the above-referenced ranges are also possible (e.g., greater than orequal to 8 micron and less than or equal to 85 microns, greater than orequal to 12 microns and less than or equal to 60 microns). Other valuesof average fiber diameter for the coarse support layer(s) are alsopossible.

Various materials can also be used to form the fibers of the coarsesupport layers including synthetic and non-synthetic materials. In oneexemplary embodiment, the coarse support layer(s) are formed from staplefibers, and in particular from a combination of binder fibers andnon-binder fibers. The binder fibers can be formed from any materialthat is effective to facilitate thermal bonding between the layers, andwill thus have an activation temperature that is lower than the meltingtemperature of the non-binder fibers. The binder fibers can bemonocomponent fibers or any one of a number of bicomponent binderfibers. In one embodiment, the binder fibers can be bicomponent fibers,and each component can have a different melting temperature. Forexample, the binder fibers can include a core and a sheath where theactivation temperature of the sheath is lower than the meltingtemperature of the core. This allows the sheath to melt prior to thecore, such that the sheath binds to other fibers in the layer, while thecore maintains its structural integrity. This may be particularlyadvantageous in that it creates a more cohesive layer for trappingfiltrate. The core/sheath binder fibers can be concentric ornon-concentric, and exemplary core/sheath binder fibers can include thefollowing: a polyester core/copolyester sheath, a polyestercore/polyethylene sheath, a polyester core/polypropylene sheath, apolypropylene core/polyethylene sheath, a polyamide core/polyethylenesheath, and combinations thereof. Other exemplary bicomponent binderfibers can include split fiber fibers, side-by-side fibers, and/or“island in the sea” fibers.

The non-binder fibers can be synthetic and/or non-synthetic, and in anexemplary embodiment the non-binder fibers can be about 100 percentsynthetic. In general, synthetic fibers are preferred over non-syntheticfibers for resistance to moisture, heat, long-term aging, andmicrobiological degradation. Exemplary synthetic non-binder fibers caninclude polyesters, acrylics, polyolefins, nylons, rayons, andcombinations thereof. Alternatively, the non-binder fibers used to formthe coarse support layer(s) can include non-synthetic fibers such asglass fibers, glass wool fibers, cellulose pulp fibers, such as woodpulp fibers, and combinations thereof.

Non-limiting examples of suitable synthetic fibers include polyester,polyaramid, polyimide, polyolefin (e.g., polyethylene), polypropylene,Kevlar, Nomex, halogenated polymers (e.g., polyethylene terephthalate),acrylics, polyphenylene oxide, polyphenylene sulfide, and combinationsthereof. The coarse support layer(s) can also be formed using varioustechniques known in the art, including meltblowing, wet laid techniques,air laid techniques, carding, and spunbonding. In an exemplaryembodiment, however, the coarse support layers are carded or airlaidwebs. The resulting layers can also have a variety of thicknesses, airpermeabilities, and basis weights depending upon the requirements of adesired application. In one exemplary embodiment, the downstream coarsesupport layer and the upstream coarse support layer, as measured in aplanar configuration, each have a thickness in the range of 2 mil to1000 mil (e.g., between 12 mil to 100 mil) and a basis weight in therange of 5 g/m² to 100 g/m² (e.g., between 12 g/m² and 40 g/m²).

For example, in some embodiments, the thickness of one or more coarsesupport layer(s) is greater than or equal to 2 mil, greater than orequal to 3 mil, greater than or equal to 5 mil, greater than or equal to10 mil, greater than or equal to 12 mil, greater than or equal to 15mil, greater than or equal to 25 mil, greater than or equal to 50 mil,greater than or equal to 75 mil, greater than or equal to 100 mil,greater than or equal to 150 mil, greater than or equal to 200 mil,greater than or equal to 250 mil, greater than or equal to 300 mil,greater than or equal to 400 mil, greater than or equal to 500 mil,greater than or equal to 600 mil, greater than or equal to 700 mil,greater than or equal to 800 mil, or greater than or equal to 900 mil.In certain embodiments, the thickness of one or more coarse supportlayer(s) is less than or equal to 1000 mil, less than or equal to 900mil, less than or equal to 800 mil, less than or equal to 700 mil, lessthan or equal to 600 mil, less than or equal to 500 mil, less than orequal to 400 mil, less than or equal to 300 mil, less than or equal to250 mil, less than or equal to 200 mil, less than or equal to 150 mil,less than or equal to 100 mil, less than or equal to 75 mil, less thanor equal to 50 mil, less than or equal to 25 mil, less than or equal to15 mil, less than or equal to 12 mil, less than or equal to 10 mil, lessthan or equal to 5 mil, or less than or equal to 3 mil. Combinations ofthe above referenced ranges are also possible (e.g., a thickness ofgreater than or equal to 2 mil and less than or equal to 1000 mil,greater than or equal to 12 mil and less than or equal to 100 mil).Other ranges are also possible.

In some instances, the coarse support layer(s) may each have a basisweight of less than or equal to 100 g/m², less than or equal to 90 g/m²,less than or equal to 85 g/m², less than or equal to 80 g/m², less thanor equal to 70 g/m², less than or equal to 60 g/m², less than or equalto 50 g/m², less than or equal to 40 g/m², less than or equal to 30g/m², less than or equal to 25 g/m², less than or equal to 12 g/m², orless than or equal to 10 g/m². In some embodiments, the coarse supportlayer may have a basis weight of greater than or equal to 5 g/m²,greater than or equal to 10 g/m², greater than or equal to 12 g/m²,greater than or equal to 25 g/m², greater than or equal to 30 g/m²,greater than or equal to 40 g/m², greater than or equal to 50 g/m²,greater than or equal to 60 g/m², greater than or equal to 70 g/m²,greater than or equal to 80 g/m², greater than 85 g/m², or greater thanor equal to 90 g/m². Combinations of the above-referenced ranges arealso possible (e.g., a basis weight of less than or equal to 100 g/m²and greater than or equal to 5 g/m², a basis weight of less than orequal to 40 g/m² and greater than or equal to 12 g/m²). Other values ofbasis weight are also possible.

In some embodiments, the filter media can also optionally include one ormore outer or cover layers (e.g., a top layer, a bottom layer) disposedon the air entering side I and/or the air outflow side O (as illustratedin FIG. 2C). The cover layer can function as a dust loading layer and/orit can function as an aesthetic layer and/or a support layer. In anexemplary embodiment, the cover layer is a planar layer that is mated tothe filter media after the charged fiber layer(s) and, optionally, otherlayer(s) are waved. The cover layer thus provides a top surface that isaesthetically pleasing. The cover layer can be formed from a variety offiber types and sizes, but in an exemplary embodiment the cover layer isformed from fibers having an average fiber diameter that is less than anaverage fiber diameter of the coarse support layer(s) directly adjacentthe cover layer, but that is greater than an average fiber diameter ofthe charged fiber layer(s) (e.g., the second layer). In certainexemplary embodiments, the cover layer is formed from fibers having anaverage fiber diameter in the range of about 5 μm to 20 μm.

Various materials can also be used to form the fibers of the outer orcover layer, including synthetic and non-synthetic materials. In oneexemplary embodiment, the outer or cover layer is formed from staplefibers, and in particular from a combination of binder fibers andnon-binder fibers. One suitable fiber composition is a blend of at leastabout 20% binder fiber and a balance of non-binder fiber. A variety oftypes of binder and non-binder fibers can be used to form the media ofthe present invention, including those previously discussed above withrespect to the open support layer(s) and/or the coarse support layer(s).

The outer or cover layer can also be formed using various techniquesknown in the art, including meltblowing, wet laid techniques, air laidtechniques, carding, and spunbonding. In an exemplary embodiment, a toplayer is an airlaid layer and a bottom layer is a spunbond layer. Theresulting layer can also have a variety of thicknesses, airpermeabilities, and basis weights depending upon the requirements of adesired application.

As described above, in some embodiments, a layer of the filter media(e.g., the first layer, the second layer, one or more coarse supportlayer(s)) may be a non-wet laid layer formed using a non-wet laidprocess (e.g., an air laid process, a carding process, a meltblownprocess). For example, in a non-wet laid process, an air laid process ora carding process may be used. For example, in an air laid process,fibers may be mixed while air is blown onto a conveyor. In a cardingprocess, in some embodiments, the fibers are manipulated by rollers andextensions (e.g., hooks, needles) associated with the rollers.

In some embodiments, as described herein, a layer of the filter mediamay include fibers formed from a meltblown process. In embodiments inwhich the filter media includes a meltblown layer, the meltblown layermay have one or more characteristics described in commonly-owned U.S.Pat. No. 8,608,817, entitled “Meltblown Filter Medium”, issued on Dec.17, 2013, which is based on U.S. patent application Ser. No. 12/266,892filed on May 14, 2009, commonly-owned U.S. Patent Publication No.2012/0152824, entitled “Fine Fiber Filter Media and Processes”, which isbased on patent application Ser. No. 12/971,539 filed on Dec. 17, 2010,commonly-owned U.S. Patent Publication No. 2012/0152824, entitled “FineFiber Milter Media and Processes”, which is based on patent applicationSer. No. 12/971,539 filed on Dec. 17, 2010, and commonly-owned U.S.Patent Publication No. 2012/0152821, entitled “Fine Fiber Milter Mediaand Processes”, which is based on patent application Ser. No. 12/971,594filed on Dec. 17, 2010, each of which is incorporated herein byreference in its entirety for all purposes.

For example, in an exemplary embodiment, the filter media comprises acharged fiber layer comprising a plurality of fibers, wherein at least aportion of the plurality of fibers are formed from a meltblown process.

The filter media may be used for a number of applications, such asrespirator and face mask applications, cabin air filtration, militarygarments, HVAC systems (e.g., for industrial areas and buildings), cleanrooms, vacuum filtration, furnace filtration, room air cleaning,high-efficiency particulate arrestance (HEPA) filters, ultra-lowparticular air (ULPA) filters, and respirator protection equipment(e.g., industrial respirators). In some embodiments, the filter mediamay be incorporated into a face mask.

The filter media can be, for example, folded, edge sealed, collated, ormolded, with or without a supporting structure, within the face mask.The face mask may be a full face piece or a half face piece, and may bedisposable or reusable. In general, face masks are used to protect therespiratory system when the air contains hazardous amounts ofparticulate contaminants in the form of solid particles or liquiddroplets that can cause impairment through inhalation. Accordingly, aface mask generally needs to provide adequate protection with goodbreathability (e.g., low resistance). The face mask may be designed tofilter dust, fog, fumes, vapors, smoke, sprays or mists. For example,face masks may be worn in areas where activities such as grinding,welding, road paving (e.g., where hot asphalt fumes are present), coalmining, transferring diesel fuel, or pesticide spraying are performed.The face mask may also be designed for wearing in hospitals (e.g.,performing surgery), distillers and refineries in chemical industries,painting facilities, or oil fields. For example, the face mask may be asurgical face mask or an industrial face mask.

The filter media may be incorporated into a variety of other suitablefilter elements for use in various applications including gasfiltration. For example, the filter media may be used in heating and airconditioning ducts. Filter elements may have any suitable configurationas known in the art including bag filters and panel filters. Filterassemblies for filtration applications can include any of a variety offilter media and/or filter elements. The filter elements can include theabove-described filter media and/or layers (e.g., first layer, secondlayer). Examples of filter elements include gas turbine filter elements,dust collector elements, heavy duty air filter elements, automotive airfilter elements, air filter elements for large displacement gasolineengines (e.g., SUVs, pickup trucks, trucks), HVAC air filter elements,HEPA filter elements, ULPA filter elements, and vacuum bag filterelements.

Filter elements can be incorporated into corresponding filter systems(gas turbine filter systems, heavy duty air filter systems, automotiveair filter systems, HVAC air filter systems, HEPA filter systems, ULPAfilter system, and vacuum bag filter systems). The filter media canoptionally be pleated into any of a variety of configurations (e.g.,panel, cylindrical).

Filter elements can also be in any suitable form, such as radial filterelements, panel filter elements, or channel flow elements. A radialfilter element can include pleated filter media that are constrainedwithin two open wire support materials in a cylindrical shape.

In some cases, the filter element includes a housing that may bedisposed around the filter media. The housing can have variousconfigurations, with the configurations varying based on the intendedapplication. In some embodiments, the housing may be formed of a framethat is disposed around the perimeter of the filter media. For example,the frame may be thermally sealed around the perimeter. In some cases,the frame has a generally rectangular configuration surrounding all foursides of a generally rectangular filter media. The frame may be formedfrom various materials, including for example, cardboard, metal,polymers, or any combination of suitable materials. The filter elementsmay also include a variety of other features known in the art, such asstabilizing features for stabilizing the filter media relative to theframe, spacers, or any other appropriate feature.

As noted above, in some embodiments, the filter media can beincorporated into a bag (or pocket) filter element. A bag filter elementmay be formed by any suitable method, e.g., by placing two filter mediatogether (or folding a single filter media in half), and mating threesides (or two if folded) to one another such that only one side remainsopen, thereby forming a pocket inside the filter. In some embodiments,multiple filter pockets may be attached to a frame to form a filterelement. It should be understood that the filter media and filterelements may have a variety of different constructions and theparticular construction depends on the application in which the filtermedia and elements are used.

The filter elements may have the same property values as those notedabove in connection with the filter media and/or layers. For example,the above-noted instantaneous resistances, efficiencies, (total)thicknesses, and/or basis weight may also be found in filter elements.During use, the filter media mechanically trap contaminant particles onthe filter media as fluid (e.g., air) flows through the filter media.

Other systems, devices, and applications are also possible and thoseskilled in the art would be capable of selecting such systems, devices,and applications based upon the teachings of this specification.

Examples

The following example demonstrates the formation of a filter mediacomprising an open support layer and a charged fiber layer, according tosome embodiments.

Sample 1 included several filter media of varying basis weightcomprising:

-   -   a charged filter media having a basis weight between 20 g/m² and        85 g/m², comprising a plurality of charged fibers having an        average fiber diameter of greater than or equal to 15 microns;        and    -   a support layer comprising a scrim and having an air        permeability of less than or equal to 1100 CFM, needled to the        charged filter media.

Sample 2 included several filter media of varying basis weightcomprising:

-   -   a charged filter media having a basis weight between 20 g/m² and        85 g/m², comprising a plurality of charged fibers having an        average fiber diameter of less than 15 microns; and    -   an open support layer (a mesh) having an air permeability of        greater than 1100 CFM, needled to the charged filter media.        The mesh of sample 2 comprised polypropylene strands having a        strand count of 5 per inch along a first axis and 6 per inch in        along a second axis.

FIG. 3 shows a plot of the normalized gamma versus the basis weight ofthe charged fiber layer. FIG. 4 shows a plot of the normalizedefficiency versus the basis weight of the charged fiber layer. Sample 2filter media demonstrated an increase in normalized gamma and normalizedefficiency, even at relatively low basis weights of the charged fiberlayer, as compared to Sample 1.

FIG. 5 is a plot of pressure drop (Pa) versus basis weight of thecharged fiber layer. Sample 2 filter media demonstrated a decrease inresistance as compared to Sample 1.

FIG. 6 is a plot of dust holding capacity for Sample 1 having a basisweight of 70 g/m² versus Sample 2 having a basis weight of 70 g/m².Sample 2 filter media demonstrated a significant increase in dustholding capacity for a given air resistance of the filter media, ascompared to Sample 1.

While several embodiments of the present invention have been describedand illustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunctions and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the present invention.More generally, those skilled in the art will readily appreciate thatall parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the teachings of thepresent invention is/are used. Those skilled in the art will recognize,or be able to ascertain using no more than routine experimentation, manyequivalents to the specific embodiments of the invention describedherein. It is, therefore, to be understood that the foregoingembodiments are presented by way of example only and that, within thescope of the appended claims and equivalents thereto, the invention maybe practiced otherwise than as specifically described and claimed. Thepresent invention is directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe scope of the present invention.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Other elements may optionallybe present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elementsspecifically identified unless clearly indicated to the contrary. Thus,as a non-limiting example, a reference to “A and/or B,” when used inconjunction with open-ended language such as “comprising” can refer, insome embodiments, to A without B (optionally including elements otherthan B); in another embodiment, to B without A (optionally includingelements other than A); in yet another embodiment, to both A and B(optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in some embodiments, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” and the like are to be understoodto be open-ended, i.e., to mean including but not limited to. Only thetransitional phrases “consisting of” and “consisting essentially of”shall be closed or semi-closed transitional phrases, respectively, asset forth in the United States Patent Office Manual of Patent ExaminingProcedures, Section 2111.03.

What is claimed is:
 1. A filter media, comprising: an open supportlayer; and a charged fiber layer mechanically attached to the opensupport layer, wherein the charged fiber layer comprises a firstplurality of fibers comprising a first polymer and a second plurality offibers comprising a second polymer, wherein the first polymer isacrylic, and wherein the open support layer is a mesh having an airpermeability of greater than 1100 CFM and less than or equal to 20000CFM.